You Can Have My TIPs When You Pry Them From My Cold, Dead Hands

We’ve seen a growing number of posts and recommendations around the net regarding components, specifically transistors. “Don’t use old parts” they cry,  “Go with newer components.”  You can often find these recommendations on Arduino forums. This all came to a head with a page called “Do Not TIP,” which was linked in the Arduino subreddit.  This page belongs to [Tom Jennings], creator of Fidonet, and one of the early authors of what would become Phoenix BIOS. [Tom] and a few others have been calling for everyone to send their old parts to the landfill – not use them, nor gift them to new experimenters. Get them out of the food chain. No offense to [Tom], but we have to disagree. These parts are still perfectly usable for experienced designers, and have a lot to offer new hardware hackers.

TIP is the part number prefix for a series of power transistors created by Texas Instruments.  In fact, “TIP” stands for Texas Instruments Power. The series was originally released in 1969. Yes, that’s right, 1969. Why are we still using parts designed when man first walked on the moon? The same reason people are still using the 555 timer: they’re simple, they’re easily available, they’re robust, and most of all, they get the job done. The TIP series has been used in thousands of classes, tutorials both online and off, and millions of projects over the years. Much of that documentation is already out there on the internet. The TIP series is also out in the distribution channel – they’ve been used for 40 years. Any retail shop that stocks a few electronics parts will have at least one of the TIP series.

The TIP series aren’t always the best transistors for the job. However, for most hobbyist-designed circuits, we don’t need the best performance, nor the best price – we’re going to use the parts we have on hand. There is always room to improve once you get the basic circuit working.

tip120In [Tom’s] specific example, he’s using a TIP120 to control a motor at 5 volts drawing 1 amp of current. [Tom’s] big problem with the TIP120 is that it’s inefficient when running the motor. That’s because the TIP120 isn’t a transistor. It’s two transistors configured as a Darlington pair. Like everything else in life, Darlington pairs have trade offs. To achieve high gain, you end up with higher voltage drop. In high current designs, that translates into heat. In this case, 2 watts of heat, which [Tom] claims will result in melted parts and fire. It turns out that the datasheet shows 2 watts is the upper limit for thermal dissipation on the TIP120’s TO-220 case. It will get very hot, but it will not catch fire. Want to be on the safe side? Add a heatsink, which is as easy as attaching a piece of metal using the convenient screw hole in the TO-220 case.

TIP-20-1ampJust for fun, we created our own version of [Tom’s] example. We connected a TIP120 to a 12V lab supply. Rather than connect a motor, we grabbed our Re:Load Pro and set it for 1 amp. We use a 680 ohm base resistor to ensure the TIP120 was in saturation. The Re:Load Pro indicated that it was indeed seeing 1 amp of current flow, at 10.9 volts. This means that the TIP120 was only dropping 1.1V, rather than the 2V quoted on the datasheet. Were we just lucky? We tried a few TIP120s we had around the lab from a couple of manufacturers, and all of them were pretty close – well below the worst case 2V. Obviously you can’t design beyond the specs called on in the datasheet, but sometimes things work out in your favor. With the current set to 1 amp, the math is easy. The Re:Load Pro was converting 10.9 watts of power to heat. The TIP120 was dissipating 1.1 watts. The TIP120 did get hot – we measured up to 60°C. But it never went beyond that. A heatsink would have cooled things down, but we were shooting for worst case scenario.  We ran this setup for 2 hours and there was no smoke, fire, or failure.

Can you do better with a different part? Absolutely. [Tom] suggests a MOSFET such as the NTD4906N. FETs are great, we use them all the time. However, they come with a completely different set of rules and pitfalls compared to BJTs. Learning the rules, the design trade offs and pitfalls of both families of devices are key factors when learning electronics design. Every component a designer learns is a new color on their design palette. On the code side we worry about people becoming “cut and paste” coders. The same thing happens on the hardware side when a designer doesn’t learn how to use different types of parts.

So don’t throw away your old parts. Use them, learn from them, and become a better designer for it!

153 thoughts on “You Can Have My TIPs When You Pry Them From My Cold, Dead Hands

  1. I have to mostly agree with Tom. 99% of the time, a TIP is used to digitally switch a load, and it’s used pretty mindlessly: take base resistor, connect to an Arduino and go. If you have a stack of TIPs you use like that (switching a load with a 3.3/5V output pin), you’re usually better off ditching the TIPs and buying a bunch of cheapie logic-level MOSFETs instead; you can throw them in even more mindless (no critical base resistor) and you usually get way better performance out of it.

    Sure, if you want to concentrate on how things work, or if you have a less generalized purpose, TIPs can still be useful, so it’s a good idea to hang on to some of them. But if you have a stack of them that you’re throwing around for general-purpose switching things, you’re better off grabbing a bunch of MOSFETs instead.

        1. The other reason to insert this serial resistor: mosfets have a high gate (no base here, that’s for NPN/PNP) capacitance, and this can be a huge load for the MCU output port while switching.

          1. I recommend a low-side driver like the FAN3111E from Texas Instruments rather than connecting the gate (with or without a resistor) directly to your uC. If you make the resistor big enough to limit the current appropriately, you’ll slow down FET turn-on and turn-off so much that the heating of the FET during the transient phase can become significant. They take care of the high current transients into the gate (including pulling current out of the gate during FET turn off), and you just need to supply a logical input.

          2. Not saying that’s not good advice, Chris, but see how complicated it’s getting already? Gate capacitance and now we have to add a separate driver. The TIP just needed a bit of metal attached to take the heat away. It’s only problem is slightly higher power dissipation.

            Different tools for different jobs, and if they’ve been selling something for 40 years, it means people have been buying them for 40 years. And that means they probably got it right 40 years ago.

            Progress helps in things like MCUs and the like, but simple transistors have been transisting the same way since forever. They’re obviously doing a good job, when so many alternatives are available.

          3. I don’t see why you couldn’t just add a voltage follower circuit in series with the output to drive a MOSFET. If not a voltage follower, but a comparator. It provides a high input impedance and provides circuit isolation incase of a short in the MOSFET. Either way if opamps are understood, it provides all the necessities of what someone would need except in the case of limiting parts but that is negated in adding in the resistors that you are talking about.

          4. The gate capacitance is no problem for the µC port. You need an extra driver only when you want/need high switching frequency – much higher than what would be possible with the old fashioned TIP anyhow.

            You can use series resistor for safety or a pull down, if you want, or if it is important, what the circuit does at power up. But you do not need it, if not.

      1. A small cap in parallel with the pull down resistor can help prevent a transient turn-on during start-up, too, as it acts like a temporary short to ground until its charged. Keep it small, mind you. Also use a gate resistor to limit gate current to a desired value (rather than depend on transistor properties).

          1. Chris said “parallel with the pull down resistor”. In this case the pull down resistor is a series resistor. ie both cap and resistor go from GPIO to GATE.

          2. Yes, but if you’re clever with your RC time constant, you can have reasonable spike protection and a delay that’s much shorter than you would want to switch anything.

          1. A zener would serve to limit the gate voltage from getting too large. However, most FETs allow Vgs up to 20V, so you are unlikely to need overvoltage protection. However, you want to make sure that the FET does not turn on when you do not want it to, hence the 5k ~ 10k resistor from the gate to ground. That will keep the FET from turning on accidentally in steady-state operation. However, start-up conditions are a whole other ball of wax. You can carefully analyze your circuit and design everything to guarantee nothing will put enough voltage on the FET’s gate to turn it on, but that is a much harder guarantee to make than you might think, as you are dealing with transients, and responses to transients, and all sorts of messes. Instead, you can just put a small capacitor in parallel with the gate pull down resistor. The cap acts as a short circuit to ground for any transients, guaranteeing you a window of time for start-up conditions to subside during which the FET will stay off.

            As I said in an earlier comment, though, a low-side driver like the FAN3111E makes a wonderful bridge between your microcontroller and your FET’s gate. These also are designed to guarantee FETs will stay off during start-up transients.

          2. Once again I would put an opamp in the circuit if the designer understands the aspects of using a opamp. Opamps are an EE’s gods gift to man if it is understood…with saying that they are typically just a magic Dorito to most people getting started in electronics.

          3. @BlurD: Do not use an OpAmp there. It does no good. It has not more output drive than the µC port (normally ~20mA). If you have special speed reqirements, than you can use a special gate driver. They can deliver real currents, from 500mA to several Amps pulses. But normally you want just one or two resistors, series and pull down.

  2. “This means that the TIP120 was only dropping 1.1V”

    That’s still a lot. I would gladly throw that away, and get a modern part.

    “The same thing happens on the hardware side when a designer doesn’t learn how to use different types of parts.”

    In other words: don’t limit yourself to TIPs.

      1. Exactly. The “Do Not Tip” article mentions only the digital domain at low voltages, which is a fraction of the possible uses for a part like that one. When used to drive a relay from say 24 volt or more (automotive or industrial applications etc) it’s perfectly fine for the job.

  3. After glancing over [Tom]’s rant, I would have to say that he should have chosen something besides a TIP120 to begin with, thus his TIP bashing is uncalled for. Had he chosen a part that *should* work for his application and it did not work when used within design parameters then he would have a valid point.

    I use (and collect) vintage parts for fixing vintage gear. I know there are folks that disagree with me, but if it worked when new it will work again with a vintage replacement.

    1. There’s also a great demand for old parts in vintage music equipment. Try throwing in a state of the art device that has high efficiency and suddenly that nice fat sounding Marshall starts sounding like every other modern amp out there – squeeky clean without personality. In the end you’ll have one very pissed off musician.

      1. I still remember doing my Tube Screamer mod. I took a $5 plastic TS-5 nobody wanted and swapped out the Op Amp chip and clipping diodes for germanium ones, plus you swap a few resistors around to get back to the original TS-808 circuit.

        I actually did the 8 pin DIP socket mod so you can try different ICs, but I stuck with the original JRC4558D (well not a NOS original, but a reissue version). There is another fight like the story here (NOS JRC4558D vs reissue): Some folks think you absolutely HAVE to have an original NOS JRC4558D nevermind that a new production reissue should sound the same. There is likely more variation in other parts of the foot pedal than in “aged” never used ICs.

        Electronic myths are kind of funny, especially in the music world where you can build an exact replica of something old and it never quite sounds the same due to individual unit variations.

  4. When I saw that page linked in /r/arduino I thought that same thing: Those negative arguments were too harsh. Telling people to throw away parts because in some use cases there are better options available isn’t a good idea.

    People have used and will use those TIPs where they are one of the worst possible options, that same applies to just about any component type/series. But that doesn’t mean there aren’t any places where they are good (enough) option.

    Don’t throw them away and don’t ask others to do so either just because you don’t like them in one scenario.

  5. I find old semiconductors to be superior to new stuff Built better, more tolerant to power sagging, etc.. There is a reason why deep space probes use old slow processors compared to the latest i7 processor. That old R3000 MIPS processor will run for 1000 years in a hostile environment, while all current processors are made to be as cheap as possible first, performance second. This makes them unreliable and freak out at the drop of a hat.

    And honestly,

    1. A good reason to prefer old IC technology in space is the bigger area occupied on the silicon by each component. Shielding against radiation is hard, and if a transistor is just tens of nano meters in side, then a single radiation particle that hit the transistor can damage it.

      1. ionizing radiation doesn’t damage Semiconductors.
        this would require change in the dopant-profile, or other physical changes in the crystal.
        but this doesn’t happen. what really happens, is that a gamma-photon creates electron-hole charge pairs inside the crstal, and can thus interfere with the Operation of the Processor. eg, it could flip a bit in RAM or a register. It could cause latch-up.
        Also, Satellites don’t really need that much processing power. There is just no need to shoot an i7 in the sky – all power-intensive calculations are made on the ground anyway.

        1. WHAT?!!!! So all that radiation hardening the military worries about and spends billions of dollars on is all for naught? OF FUCKING COURSE IONIZING RADIATION KILLS SEMICONDUCTORS!!! Look up only about a billion whitepapers on the subject. And it gets worse the thinner and smaller gates are getting. Wow…. and “fubar” is pretty fucking military. But you obviously know dick about electronics. And on the subject of satellites, there is a reason they still prefer tubes in space, and it aint because the filaments make nice heaters for the cold of space….

          JUST WOW.

          1. lol, we have all levels of experience here from the most experienced EE’s (even, people like [Bill Heard]) and also even those who are just starting out. So be kind! or the people you insult today *won’t* design the instrument that save your life in old age. OK Just kidding. Be kind anyway – it shows good character.

          2. of course its a problem. never even argued with that.
            But i stand by what i said: beta/gamma radiation does not damage the semiconductor physically! They just knock loose a few charge pairs, that interfere and disturb with normal operation. this can of course lead to malfunction, and blow up a rocket.
            However, neutron or protons, alpha particles etc… CAN alter the silicon-crystal, and thus destroy the chip. But at least protons and Alpha-Particles can be shielded easily.

          3. Actually, smaller and thinner means smaller probability of capture, be it photon or particle…there was concern that “new” (this was in 90s) high density RAM would be very susceptible to having bits flipped by radiation, which turned out to be wrong…newer RAM performs just as reliably as the old one, but eats less power and dumps less heat…

            p.s. name one fucking satellite that still uses a vacuum tube, even just one. Seriously. I want to know who makes tubes durable, reliable and efficient enough that they put them is satellites.

            p.p.s. unless your satellite is a deep space probe, it’s more likely to encounter problems with getting rid of heat rather then not having enough of it…

        2. That’s simply wrong – ionising radiation does damage semiconductors; over time it can damage the NP junction causing a locked on of off state
          The reason power intensive calculations are done on the ground is _because_ there’s so little processing power available on the spaceccraft.

    2. Those R3000 are a very special versions of standard R3000, and they cost something about 50 grands if I recall correctly.If you’d throw a regular R3000 into a deep space probe, it lasted just until the first pass through Van Allen’s belt.
      Make the i7 the same way as the radiation hardened R3000, and it will last a few hundred years too. OK, it won’t, but you’re comparing apples and dogs.

      1. What about the venerable RCA 1802 8-bit CPU? Used in spacecraft and everything else from Chrysler ignitions to cell phones. Not a $50,000 part and still functioning, providing that the caps in the power supply are still holding out.

        1. “The spacecraft was controlled by six RCA 1802 COSMAC microprocessor CPUs: four on the spun side and two on the despun side. Each CPU was clocked at about 1.6 MHz, and fabricated on sapphire (silicon on sapphire), which is a radiation-and static-hardened material ideal for spacecraft operation”

          https://en.wikipedia.org/wiki/Galileo_(spacecraft)#Command_and_Data_Handling_.28CDH.29
          https://en.wikipedia.org/wiki/RCA_1802

          Looks like many craft were using specialized SoS versions of the chip, not just a commodity version.

          1. Well, how do you like that… According to my RCA COS/MOS Memories and COSMAC Microprocessors Databook from 1979, Silicon on Sapphire (SOS) was the norm for the line of COS/MOS products.

            I’ve always wondered about that deluxe version they used in spacecraft with silicon on sapphire but I could never find a model number that differentiated the regular ones from the SOS ones. This afternoon your post prompted me to crack open my RCA databook and there it is on page 6, paragraph 2 where they describe SOS (silicon on sapphire) in the COS/MOS lineup not for radiation hardening but to improve component density. The following is the full 2nd paragraph:

            In addition, the cost competitiveness of RCA
            COS/MOS integrated circuits is maintained
            through continued innovative advances in design
            technology. For example, the inherently larger
            number of transistors in COS/MOS integrated
            circuits (in comparison to equivalent NMOS types)
            is compensated through the use of increased
            packing densities made possible by C²L and SOS
            technologies. C²L (closed-cell logic) is a high-density
            technology that eliminates the need for guard bands
            through the use of closed-cell transistors.
            SOS technology, in which silicon
            transistor islands are forms on a sea of insulating
            sapphire, can improve packing densities ten-fold
            in comparison to standard metal-gate logic with a
            simultaneous increase in operating speed.

        2. There’s cellphones with 1802s onboard? Interesting! Are they just farmed out, part of an I/O chip somewhere to scan the keyboard or whatever? Do they do real cellphone work?

          1. Yup, I don’t recall the brand but they were those “in-car” cellphones; the ones where the transceiver was mounted under a car seat and they had a full on handset with a curly cord attached to them. They were Audiovox or Craig or one of those brands. I used to wonder why RCA never really chased the home or business computer market but once I saw how well they were entrenched in industrial electronics I understood why.

            You can even buy new ones (Intersil). I think they’re about $100 each in volume so I don’t expect anyone is specing them for anything new. I think I bought mine in 1980 for about $25 which was a reasonable amount for a CPU back then. Every now and again they come up on EBay and you can get them in quantity for anywhere from $2 to $10 each.

          2. Ah OK they *were* used in cell phones! I was thinking it would be pretty bizarre in this day and age. How do you even port Android to an 1802 anyway?

            On unrelated news, I had a dream last night about a primitive games console. The lesser-known ones that came out just after Pong, stuff like the Signetics 2650-based ones. This one was an imaginary one that seemed really familiar. I used to collect old computers and stuff.

    1. A former employer of mine was tossing out a bin (~1x2x3 feet in dimension) of Power transistors that had been used in testing (environmental extremes and MTBF) I wish I had scooped up a gallon of those before they hit the dumpster. I’m sure there may have been MOSFETs in the mix.

        1. What “..boring comfort zones we weave” ?
          Nah & avoid diversity, unintended consequences for those odd ball kids toys designed solely to use up old stock from a Chinese contractor at Sham Shui Po (HK) manufacturers.
          Recall getting a nice bunch of parts on my last visit to HK, entertaining for my 10-13yr olds then having them exclaim “dad, these 5v zener seem to have a discontinuous bilateral memory effect – we could use it to fake some sort AI like impression – wtf !”…
          *grin*

    2. Will you – no.

      Should you? Yes.

      There’s the economic case to consider, because the continued use of the old devices means people buy lots of them and don’t buy the better parts, which remain more expensive and difficult to source in quantity because there aren’t made in such volumes. That means less spill-over onto the hobbyist market as well.

      1. I doubt hobbyists using these parts would have a big impact on the large production world. Even if an obsolete part is used in prototyping, once demand justifies mass production, it’s likely worth redoing the circuit anyway.

  6. I mostly agree on his point of not using tips for Arduino load witching. However, if it works, it works, who cares about the Watt of wasted power. It’s not like going to be mass produced and foster global warming.
    But there is a second point: while a logic level FET can usually only be used for switching,the TIP can also be used for analog duties. Its Base-Emitter Voltage is defined and it will not oscillate in a current feedback circuit like a highly optimized switching FET will. Hence, you can make much more with the TIP than with the FET.
    But in general, of course, one shouldn’t use parts unfit for the job.

  7. There may well be an interesting parallel here re biological evolution of parts to fit the purpose.
    ie. The parts were brought onto the market long ago and fit a purpose, ie The market
    exercised its selection criteria which is a combination of issues which make them fit for a range of applications of course including economics (energy issues) – much like a particular protein or even an ancient life-form, it still has a place now but, need not be re-adapted to fit something else. This doesn’t mean it will or will not be useful in the future, it isn’t a deterministic scenario, it all depends and that is a huge dynamic. ie Everything moves all the time and that applies to the abstract as much as it does to the tangible.

    The trend suggests there will be an ‘encompassing’ which could reduce diversity significantly as more equipment, systems & products become monolithic and may no longer be built from individual parts ie The suggestion is they will be print-like fabricated as smooth unitary parts that cannot be repaired, their cost will be low, the energy used is reducing vs the complexity & utility but, for those interested in education & history many parts will have their uses – if at least in the long term as pointers to how progress and change unfolds and stimulus for the imagination too…

    For the time being and for the foreseeable future I will continue to use these parts and other even older ones, even the lowly axial 1% metal film resistors – Eeegads !

      1. Admittedly, I get a bit sidetracked from time to time observing many of nature’s patterns repeated throughout human design/speculations etc and there are so many repeating patterns which are similar in kind though not in scale but, I’m in Perth, Western Australia and not acquainted with acronyms used outside my parochial influence, other than so an update on “HAD” would be helpful – did you mean a Heuristics AI development blog as have an interest in obverse AI (sry US only 2% of the world for me as too much to do locally)…
        Cheers

      2. Yep, my mind started to turn to mush too.

        I think I understand what you are saying though and I agree. I am not sure where you were going when you said “The trend suggests there will be an ‘encompassing’ which could reduce diversity significantly as more equipment, systems & products become monolithic and may no longer be built from individual parts ie The suggestion is they will be print-like fabricated as smooth unitary parts that cannot be repaired,…”. I think you will always have hobbyists using discrete components. The issue is not just old vs. new as Adam pointed out. It is also “works well enough” vs. “does not work at all” and correct vs. incorrect. That is not always cut and dry. Sometimes a FET is not better than a TIP.

        1. “Yep, my mind started to turn to mush too.”

          Mike may unintentionally be trying too hard to be ‘wordy-wise’, instead reads quite disjointed and very ‘bot-like’.

          Mike (assuming you really are not a cat/paste bot), draw us in with your words; don’t force even an avid reader to skim the sentence for a rough gist. Someone thinks you should write a ‘HaD’ article – I suggest to take time at the formatting stage.

          1. Nah, Mike Massen is just an incoherent and condescending asshole with an inflated opinion of himself. Seen him on many other forums; he has a rather consistent habit of quoting other people by ascribing the with insulting actions like, “James mumbled confusedly: -quote- “, whenever he finds himself answering to people who know better.

          2. Thanks to Deyessorc & to Kevin I offer:-
            Hmmm, upon reflection my post didn’t pan out well, I was attempting to describe a potential arena we seem to be moving towards globally & vainly attempting to cover depth of opinion – sorry case of qty of sublime red wine whilst straddling several open forum tabs, apologies.
            In respect of “encompassing”
            Although bulk of hobbyists appear to be very comfortable with discretes, I’m a professional electronics engineer of >30yrs diversifying & sometimes with older commercially available discretes (happy to use earlier BJTs but mindful of thermal runaway etc) to teach & explore diverse uncommon circuit topologies but, acutely aware the global high end production environment is trending towards a sophisticated 3D print like manufacturing model from a great deal of discrete steps (& such components) to a monolithic unitary format speeding production whilst attempting to significantly reduce material handling.
            Eg. Been suggested long before I took an interest, that products such as smart phones could have all sections/semis etc, active & passive, printed/bonded onto & integrated with enclosure structural components in a mostly seamless methodology & in a mostly single fabrication step.

            Overall infrastructure expense of such an approach, in concert with product finished cost, is products won’t be repairable (except maybe by enthusiasts or hacked) & in conjunction with materials will approach 100% recyclability. I’m also on a few parts brokerage forums and see many end of product run stock blocks offered, I don’t see that changing in the medium term but, the driving of Foxcon & the like is pushing the limits and that will bring the cost of infrastructure equipment down too. ie Right now its not feasible to make our own TIP120’s however, if what I observe re major advances in material manipulation comes off well, it might be possible to re-craft a comparatively short run by an efficient fab-house according to early published specs even back to old germanium devices and dare I say it later on we can acquire a “universal functional device” 3D printer, though other uses for than TIP120s etc will abound.

            With the wide spread of projects available to me its increasingly difficult to offer generalizations without getting concerned at readers experience & education, so can become wordy as so often simple speak can be misinterpreted by the impatient & angry as condescending. I will attempt to be more succinct in future, red wine allowing ;-)

            ps: @gregkennedy, I guess it seems obvious to most acronym ‘HAD’ should really mean “hackaday”, don’t favour those contractions as they aren’t singularly precise especially as posting space easily allows the full word without diverging to other possible meanings for those who frequent cross-discipline forums getting exposed to so very many acronyms so often.

  8. Lets see… The power driver in the TIP120 saturates at about 0.4V or a tad below at 1A, since much of the 2V spec, or 1.1V in practice, is the high VBE in saturation. Using a different configuration would greatly reduce the dissipation. The issue is that it is a Darlington.

    FET’s have their own issues, and are often not the best choice for reasons of dissipation, especially with loads that are switched at high speed, and take a greater depth of knowledge to design with. Most of us have experienced the result of poor design with power MOSFET stages in commercial products, nominally designed by people with the experience and knowledge.

    With the bipolar option, efficiency may be a little lower, though not always, but for casual work, students, and hobbiests, the reliability will win.

  9. It would be extremely useful if either author actually RTFM. Seriously. It’s not that hard to read the collector-emitter voltage diagram in the linked PDF and extrapolate it down to 1A, which allows you to assume a voltage drop of about 1V. I’m astonished by the incompetence displayed in public here.

  10. Quick… Everybody…

    Throw out your hacksaws and get your very own plasma cutters.
    Throw out your repraps and get a Stratasys.
    While you are at it.. go gather some rocks. Throw those away too! We all need to be doing our part to fill the landfills. Those are our grandchildren’s golf courses and ski resorts in the making!

    If it isn’t the newest and best then you shouldn’t be trying to use it.

    1. If everyone who ever needed a hacksaw were to suddenly demand a plasma cutter, the prices of plasma cutters would actually plummet because manufacturers would rush to make them in great quantities. They’d also probably rush to develop cordless battery powered plasma cutters, etc.

      The biggest thing holding the future back is that the past is still good enough.

      1. The opposite would be true…. high demand relative to supply would mean the retailers could ask for a higher price and get it… regardless of what the actual cost was from the supplier. Also, there is lag in the price. Suppliers have to retool for higher volume production, and that takes up-front money, as well as time. But once everyone has a plasma cutter, the market drops out and the suppliers get screwed. Then it shifts to a maintenance product model.

        1. No. It would actually shift to the cordless drill model, where after the initial rush to sell everyone a product, the market will be quickly overtaken by cheap inferior products – which nevertheless fill their function because most users don’t subject the tool to heavy duty work.

          Once everyone who needs one has one, the one who makes the cheapest replacement for the broken units gets all the business, and so the race to the bottom starts.

          Just as today you can buy a $20 cordless drill that works adequately, you could buy a $20 plasma cutter that cuts whatever some hobbyist who is happy with the $20 cordless drill would need it for.

      2. that logic only works if everyone on the entire planet who needed to do any kind of cutting at all were to buy plasma cutters.

        you are discounting all of the different uses and situations one finds oneself in, a plasma cutter is a very specialized tool and it wont cut your bagel.

        1. Not all need to change over to plasma cutters – just a sufficiently large number of people.

          It triggers a “gold rush” where the manufacturers scramble to produce large volumes of a product to cash in. This causes competition, and when the market matures the prices will plummet down.

        1. The propensity of people to stick with the old because it still “works” is a horrible thing.

          Like, “Oh, this old nuclear powerplant? Naaah, it still works, we’ll just extend it for another 20 years.”

  11. I’m with the reuse club. I have electronic parts that was new when I was still in diaper and they are still used 40 years after it was made.

    Sometimes I may need a part NOW and even back in 80s Radio Shack often didn’t have the right stuff on hand so either I get to use whatever similar part, however old it is, or wait 2-3 weeks for a new one.

  12. I am unsure about the peak current capability of the arduino/atmega but I wouldn’t recommend direct switching of a 2 nF input capacitance mosfet as the linked article suggests. Even if you use a mosfet driving IC you would have high charge/discharge currents on your board. You’ll have to be aware of these while designing your pcb, this is not the case for BJTs. So every technology has it’s advatages and disadvantages and only by learning those, one can properly design circuits, so I totally agree with Adam.

    1. No problem for your average LED PWM. That gets interesting, when you reach a switching frequency of 100kHz or above. Then you need some kind of gate driver. This is of course no problem with your darlington BJT: It will not switch that fast at all :-)
      If you want to limit the peak gate current you can use series resistor of several 100 Ohms. This can improve EMC, if that is of concern in your project.

  13. This seems to have hit a nerve! I don’t throw out my old semiconductors. I even still have a Z80 chip and some very old semiconductors, but I keep them largely out of sentimental value. Modern semiconductors are so cheap and capable that I only use the old stuff when I don’t happen to have a suitable modern device on hand. The world won’t end by doing that but I suspect the advice was intended for those without the knowledge needed to safely use older semiconductors that often have higher power dissipation. Having said that, modern MOSFETs still need to be used with care especially when switching high currents at high speed.

      1. Grab this :-
        hc-ddr.hucki.net/wiki/lib/exe/fetch.php/elektronik:z6871_rom.zip

        Apart from that you need –
        1) the original chip spec from Zilog
        2) the replacement chip spec from Zilog
        3) Someone to design a board (it’s an easy one)
        4) The replacement chip
        5) A FLASH chip or EPROM
        6) A programmer
        and your done.

        This is HAD, you will find someone to help, just ask.

        I can do the board design but I’m not the best. I have a programmer (of sorts).

        The only thing that is hard to get is the ZIP above.

    1. What do you use that particular model for? Do you need the “high” breakdown voltage? You could get a model with an order of magnitude less drain-source resistance, at equal or less input capacitance and for the same price, especially if you’re buying from Mouser.

      1. I agree, I was using the IRF640 in a project (because they were available locally) and kept burning them up despite having modest heatsinks on them. I replaced them with whatever is available on Sparkfun and they never even got warm to the touch.

        I suppose it really depends on the application though. You sometimes see the IRF series specified in old linear circuits where it probably doesn’t make any difference.

        1. That sounds like the wrong part for the project or the support circuitry was out of spec for the devices you were using.

          I built an H-Bridge a few years ago but I didn’t have the BC557s or BC547s or whatever was called for so I substituted some general purpose NPN’s and PNPs I had kicking around. The circuit worked but my transistors were getting really hot and they would have burnt up for sure. I adjusted the values of the resistors in the support circuitry and everything settled down. Like yours, they don’t even get warm now.

          1. In that particular case it was the wrong part purely due to the excessive heat without much airflow available, although I will readily admit to blowing up MOSFETs (and other nearby components) with improper drive circuits on other occasions!

          2. I can relate… Prior to solderless breadboards and more resilient components, I don’t think single a FET ever survived me and my soldering iron. I was resigned to using general purpose switching transistors and sockets for anything the least bit sensitive.

        2. Used the IRF840 series for an Australian auto cig lighter inverter, circa 1989/90. During development the devices had a propensity to overheat when they *shouldn’t* based upon situation re thermal resistivity, current flow etc. Turned out these devices and IRF640/540’s, which I used in a motor driver, had immense propensity to spurious gate oscillations – ie they wouldn’t turn on cleanly and went through extended linear modes whilst oscillating. Almost impossible to manage in any breadboard environment re many stray coupling topologies…

          ie That & undamped current mode reflections across the devices driving a high voltage caused spurious switching oscillations of up a MHz or so despite comparatively high DC appearing gate capacitance… A gate series resistor in conjunction with ferrite bead (or 2) on the gate lead/resistor and snubber caps/MOVs on the high volt switching side in a tight pcb layout was like chalk & cheese ie No more overheating at all despite fact the power delivered was the same or even more.

          Resulted in the Mypower range of inverters and sold > 4000 over a period of 12months. Unfortunately the production crew, assuming no visible static spark = no damage, got slack re ESD precautions, that and the Ceo not paying any rent for over a year, reselling repaired inverters as if new & swallowing revenue on expensive crab lunches/dinners, booze (grange) & escorts guaranteed the failure of the enterprise. That and the naive hubris of telling everyone across Australia on national radio we couldn’t keep up with demand also just before he swallowed investor funds to ramp up production signed the mass market death knell as so many others brought devices from Taiwanese variants, the combination created enough substantive threats the Ceo dumped it. Of course one can imagine how someone not acquainted with risk assessment issues passes blame, negligible royalty that year :/

  14. “New is good, old is bad” – what a load of hogwash!!

    This diseased thinking often pervades the engineering world, usually originating from the marketing / financial types. I think a quote by Bjarne Stroustrup sums it up nicely, and although he was talking about software, not hardware, the principle is the same…
    “‘Legacy code’ is a term often used derogatorily to characterize code that is written in a language or style that (1) the speaker/writer consider outdated and/or (2) is competing with something sold/promoted by the speaker/writer. ‘Legacy code’ often differs from its suggested alternative by actually working and scaling.” – http://www.stroustrup.com/bs_faq.html#legacy

    (Bjarne designed the C++ programming language)

  15. Umm, Any bipolar is going to have some (significant) voltage drop in common collector mode. The normal ‘fix’ is to use a second small bipolar in open collector config driving the power bipolar in common emitter mode and in that case you probably wouldn’t want to be using a darlington for the power transistor.

  16. Stop blaming the TIP! It’s the Darlington-configuration that has high losses.
    But there’s truth to the TIP series being mediocre BJT’s, low hFE, sluggish switching times etc.

    1. Here, here!

      Not all TIPs are darlingtons. I keep some non-darlington ‘TIP31C’s and ‘TIP32C’s available at all times. Agreed that they’re old and slow (I’ve got better BJTs around too), but they’re also indestructible and good enough for a wide very range of uses.

  17. That reminds me of the first power supply I ever made over 50 years ago. It was with tubes from a TV that I had salvaged. It worked but only lasted about 30 min before the tube gave out. It was a good lesson on how to read and understand the RCA tube manual. So even when you use old parts there is education involved and lessons learned. I am still at it and sometimes I even let the magic smoke out.

  18. BJTs are still useful in modern designs. You have to know where to use them. Unfortunately, the linked website hasn’t even thought about these use cases. Fact is, BJTs are cheaper and more available in convenient sizes, and there are quite a few cases, particularly with 3.3V or lower voltage parts, where they’re actually far easier to drive with cheaper parts, and the voltage drop tradeoff is acceptable. There’s no mention of MOSFET turn-on voltages and drain resistance vs voltage, which is a common problem when you go 3.3V or below (which is really common in any modern 32-bit microcontroller). The part he specified, for example, does not work with a 3.3V uC.

    With BJTs, if you have to switch a really simple load, usually in the <1A range, you only need greater than the base-emitter diode, 0.7V to turn it on. There are low voltage level MOSFETs, but they're often not easy to shop around for and don't come in convenient (thru-hole) packages. I've found in quite a few situations, typically when you're switching higher voltage loads (3.3V switching a 12V LED string, for example) BJTs end up being cheaper and a good cost tradeoff. There are also new low-VCE BJTs, which ended up being the optimal device for an adjustable battery load, for example.

    Additionally, if you're a beginner prototyping anything high power, a BJT can be safer to use as you don't need to worry about blowing the gate. I'd still probably prefer starting with a TIP12x/TIP11x for any higher voltage motor drive applications (at 12V, the numbers won't look nearly as bad, if it's not obvious yet)

    Ditto to the problem being the Darlington configuration, though. It existed out of convenience; you can always cascade a common emitter switch if you need better performance. Not every BJT in the TIP series is a darlington. I'd agree that the TIP120 shouldn't be used in as many places as most people specify these days, but I'd have some pretty strong disagreement with the 2N2222/equivalent small signal BJT on that list.

    The "alleged circuit" is also probably not one which a reasonable EE in the 70s, 80s, or 90s (or engineer any other decade, actually) would have ever recommended. It's just one that gets floated around a lot of Arduino / hobbby / novice forums. That schematic should probably die. Most experienced engineers know about this efficiency issue, which was why separate power and logic rails were common, and your motors would typically be wound to work at 12V or 24V – at those voltages, the efficiency of the switch at the worst case 2V goes from about 40% (at 5V rail) to 83% and 92% at 12V and 24V respectively. In fact, at higher frequencies and higher voltages, you might find that the switching losses from a MOSFET can rival the fixed voltage drop in a BJT (though that's not common in hobbyist designs, fo course)

  19. Don’t throw those old devices away. Genuine vintage semiconductors (especially high power devices) go for a premium. If you compare the die’s from a genuine power transistor (BJT or FET) to one you get from ebay/china, you’ll quickly discover why.

  20. Having just spent an evening cleaning polishing and shellac-ing a spirit level made in the 1890s, I turned an old dirty lump of wood and dull metal in to a shiny polished rosewood and burnished brass functional and attractive conversation piece. Should I have simply thrown it out because I can get a new one from China for a dollar? … that’s the logic here… throw it out there are better toys out there… I have bins full of BJTs, bins full of FETS, old voltage regulators.. all manner of *stuff* and I buy new *stuff* all the time. If I need a TIP42 for a repair, I’m not about to go and redesign the circuit to use something else.. Rant all you like, I’m going to hang on to all my stuff.. no doubt most of it will go to landfill when I do, and I doubt if any of it will still be around in 120 years time, but you never know.

    1. Not to worry. Last year I got a load of old components from a guy that passed away. I was able to keep more than 2/3, and it will be definitely useful. Some people can see past this “old is useless” play.

      1. I inherited a load of stuff the same way nearly 30 years ago. The fellow was an old time technician. I still have a few boxes of parts, mostly precision resistors an caps but there are also a few super old Silvania transistors and old ICs in circular TO5 shaped packages. The other parts like 4000 and 7400 or 555 and Linear ICs have found there way into lots of projects over the years. The only parts I worry about are older caps, anything silicon seems timeless and works as well today as it did when it was designed.

  21. This is all a total crock of ####.

    The thickest book you would find in an electronics workshop before we had the net was the ‘Transistor Substitution Manual’. I good engineer not only could find the right transistor for the job but could also offer some alternatives.

    What does old mean here when you talk about ‘old transistors’ do you mean the ones made to a specific specification 20 years ago or one made to the same specific specification that is rolling off the conveyor today? They’re NOT numbers for transistors!, they are numbers for a *specification*. The only difference between the ‘old transistors’ and ones made to the same spec today is that the old one will be somewhere within a specified range and the new one will most often be very close to the typical value within that same range. And as someone mentioned the die size is often smaller now.

    And what of the suggestion that by not using ‘old’ parts the price of new parts will fall. It’s suggested that by using a FET in the place of a BGT will cause a drop in the price of the new FET’s. What a crock! If you need a BJT then you use a BJT, if you need a FET then you use a FET! BJT’s don’t make good high speed switching transistors and FET’s don’t make good linear regulators.

    yeah, so I call total BS on this one!

    The whole premise is based on the age of physical transistor when the reality is that If they’re still being manufactured then the specification is still current.

    1. Sorry about the BGT. Giving consideration to recent news … a BGT is obviously a Gay Bi Transistor … not to be confused with a Bipolar Junction Transistor. BGT’s are much better at amplifying colors.

  22. My personal favorite is TIP122 (higher voltage rating than 120). I use them for virtually all loads that require 1A or less (motors, relays, small heaters etc). With MOSFETS I had a problem with high required gate ON voltage for few projects (12 V). Considering that supply voltage was 5V, that was a no go. And regarding old parts … earlier this year I built regen receiver with 6SN7 tubes. Earlier experience also showed to me that the most useful semiconductor parts are small signal universal NPN transistors, and diodes.

    1. I work for a company that sells vacuum tubes. Believe me when I say that the field is ALIVE AND WELL. And not just for audio tubes. Sure, we ship out hundreds of 6SN7s and 12AX7s a month, but also tons of standard tv, radio, horizontal sweep, power tubes, etc.

      It is definitely more of a hobby for most of our customers but no one has ever suggested throwing away the tubes because the tech is old.

  23. It seams to me the person writing the article never has done real product design. There is a time and place for everything. I design battery management systems with BJT’s to help reduce heat buildup in singular parts and help share load.

  24. Tom is, at best, an idiot. At worst he’s looking for attention with a headline grab.

    I don’t need to reiterate all the good reasons to use (or at the very least learn) TIPs. We’re all also aware that there are newer and in many cases better options. But when applied to ANY other field this argument falls to pieces.

    So my 2gb and 4gb thumb drives should be immediately scrapped too? Any obviously any IDE hard disk under 750GB. Hey, I have a P4 running as a media center… I’ve gotta go drag that relic to the curb and replace it with an I7 stat! Wow Tom, I never realized how much junk I have here.

    Hey Tom- Do us all a favor and step away from the soldering iron before you hurt yourself.

    1. Well, something can be said about the P4, to be honest… it kinda depends on a lot of variables, but it may be feasible to replace it with a low-power Atom or I3 or (if your application allows it) a RPi2 or so. It will cost you some money to get a new one, but dependent on use, you may get it back in the long run due to lower power usage.

  25. Stop hating the TIP and learn to read/interpret specs instead so you can choose the right component for the job. I think the author nailed it with his comment about cut and paste on the hardware side. Good circuit design takes a bit of thought and understanding about how the circuit is supposed to work and how the components work within the circuit.

  26. We youngsters need those parts to learn. The old guys have experienced the whole history of semiconducter tech while we started with a Intel 286 PC or even younger.

    Let us make our own mistakes and realize when a newer design is better for our problems.

  27. I just finished reading Tom Jennings article, and so far, I can come with this conclusion.

    1) If you alredy have TIPS, use them, but let it be known that it is not as efficient as MOSFETs
    2) If you are going to buy Transistors, buy MOSFETs.

    Since when is hackaday and slashdot a delicate flower? Is this some sort of new world trend?

    But thanks for pointing out this article. Before it, I didn’t even knew that Tom Jennings existed. Now I will become a big fan of his website.

  28. I just finished reading Tom Jennings article, and so far, I can come with this conclusion.

    1) If you alredy have TIPS, use them, but let it be known that it is not as efficient as MOSFETs
    2) If you are going to buy Transistors, buy MOSFETs.

    Since when is hackaday and slashdot a delicate flower? Is this some sort of new world trend?

    But thanks for pointing out this article. Before it, I didn’t even knew that Tom Jennings existed. Now I will become a big fan of his website.

        1. His blog was written “rant style”, but some people here are taking it a bit too personally. He’s only suggesting that people doing those small forum projects should use some of the better, more modern parts if you are going to buy them anyway. Not that everything should use FETs or that BJTs should disappear; it was clear that was takling about very simple switching applications like those tutorials on switching LEDs/motors/relays/etc. with arduinos and whatnot. He wasn’t talking about RF, or trying to steal everyone’s vacuum tubes and 555’s to burn them in a furnace.

          Do you usually use the TIPs he was talking about to amplify VHF from 0.9v supplies? :D

          No one is going out of their way buying 741s other than for repairs or clones of some antique stuff. The same can be said formost of the TIP series, save them for repairs and projects that depend on their behavior. They are not that cheap anyway (at least where I live, modern counterparts are similar priced/cheaper). There are plenty of modern, high performance BJTs out there and if you are using an arduino/etc. for learning purposes, might as well learn about the “newer” and more efficient ways of doing things. MOSFETs nowadays are also a lot better and more forgiving than the old stuff.

          Take the comedy bits away of his post and I can’t really disagree with the sentiment.

  29. My parts chest has a drawer marked “harvest”. Without it I would have spent a fortune on shipping. Using old parts not only saves money, it saves fuel and lets us take share in a tiny amount of co2 prevention.
    The downside might be poor chinese people not finding a job, but I’m not really convinced about that…

    1. I do not think of some CO2 in this and also not that much about money, but If I want to do a project or repair on Saturday afternoon I am very happy about some ‘harvest’ and junk boxes and some old PCBs lying around, where I can – perhaps -find a useful part. It is the saved time, that counts.

  30. Wow. Ok. I’m on vacation I should not be reading nvm replying to so much silliness.

    First, though I thoroughly defend my rant, seriously calm down y’all, the tone was intended to be humorously over the top. I guess Americans really don’t do irony.

    Second, I did state “for rule of thumb of construction” etc not telling actual EEs their job. Really, for many people doing their first largeish load driven by arduino modern MOSFETs are …. On never mind why bother. But inflicting 70’s parts on newbies is simply cruel.

    Last, argue emotion against physics and ohms law (re: dissipation, drive requirements, et all you want if it makes you feel better.

    Enjoy!

    PS: im a huge nerd for historic gear, check out my previous website worldpowersystems.com so that’s not a fair crit. Sheesh.

    1. so you dismiss the dismissive attitudes in like manner?

      what people have been arguing makes plenty sense if one wants to read, plenty of people simply noted how your “rant” (how one can call it that and expect people to take it seriously is beyond me) glossed over several factors that should decide ones choice in transistor, something you yourself seem to know, so why the attitude(“oh never mind why bother”, “last argue emotion against physics and ohms law”)?

      if it was intended for the the newbie and only the newbie perhapos that should have been made more clear?

      havent really seen anyone arguing directly with emotion here, might be an oversight on my part, i have seen the first 15 differing reasons, ranging from i had it on hand, to there is a very specific reason why i chose a TIP over a FET.
      but none that directly said this has to happen because that is how i feel it should happen, there are some that have argued emotionally, but the argument isnt emotion.

    2. You know what makes a hobbyist a hobbyist? That they do it part time, in their spare time, for their own personal enjoyment. Rather than having had the professional education and training plus the 40 hour work week for years to hone these skills, the knowledge is self taught in a compressed manner and executed “on the fly” through experimentation. It isn’t just you and your humorous over the top rant, many others have taken the occasion to slam the hobbyists as intellectual inferiors who haven’t spent thousands of hours on education and training to do it like a pro. While wholly not your fault, it invited the occasion. This level of component snobbery is seriously off-putting to the individuals who do this kind of thing for fun. Off-putting enough for some to put down the soldering iron for good and go do something else with their free time. May I suggest that if you really think it is a serious problem, a much more constructive focus of your energy would be to get out there and create better education materials for the hobbyists.

    3. >First, though I thoroughly defend my rant, seriously calm down y’all, the tone was intended to be humorously over the top. I guess Americans really don’t do irony.

      Considering that your (comedic in intent) use of capslock, multiple exclamation points, and phrases like ZOMG/wtf are things used by a worryingly large amount of netizens in an unironic manner, we really had no way to tell.

      If you spend some time on places related to development boards like the arduino or security auditing systems like Kali, you’ll find that individuals with a lacking grasp of formal language and a tenancy to overreact are in large numbers.

      I seriously didn’t see TFA as satire in any form during my first read through, just as poory thought-out hyperbole. Maybe this is a sign I need to stop hanging out on IRC channels filled with emoticon-spewing newcomers and spend time with normal, well-adjusted adults.

      Perhaps for future excursions into humorous posts like this, try using some of the numerous sarcasm punctuation available. https://en.wikipedia.org/wiki/Irony_punctuation

  31. The advice to throw perfectly serviceable parts into the landfill is shameful. Especially if they are still new and unused. Don’t we generate enough waste already?

    Those parts are available, cheap, and they work. What’s the problem? Sure there are billions newer devices available that are faster, more efficient, yada yada. So? Select specific part for a specific application when the requirements call for it. An awful lot of the time the situation is not so critical and anything on hand will do.

    I have a two or three electronics stores around here, thank God they are rare things now a days, with piles of not so new devices in stock. They get newer things too but the suggestion that they empty their shelves in to the land fill is nuts. Meanwhile they are a great resource to have on hand everyday.

    What’s wrong with learning about the things you are using?

  32. Us guys that have to keep old hardware running that CANNOT chance the existing circuitry would like to punch tom in his fucking face for making parts that are STILL USED AND STILL NEEDED regardless of their obsolescence more and more scarce. New circuit, new design, new parts. But old design and you hands are tied to a fucking spec? Fuck you tom.

  33. I agree with the comments that understand it has nothing to do with TIPs in general, but it is the darlington configuration of the TIP used. Not all TIPs are darlingtons.

  34. How’s about a list of drop-in FET or similar replacements for the nasty old TIPs? Or a guide to re-engineering things to replace TIPs and 2n2222’s etc. etc. so commonly used in a million hobby books and circuits since the year zero?

  35. There are times when bipolar transistors are simply better – less prone to ESD, more or less constant on-voltage drop can make them better for high current operation ( one of the reasons they are still used in brand new designs). MOSFETS also have high hard to drive gate capacitance/miller capacitance (one of the reasons BT are used in RF).

    The cost of power MOSFETS has come down where it doesn’t matter much. There is an attraction to avoid the base input resistor – but often you still need one for a MOSFET if your design considers ESD hitting the gate.

    What he should have said is the the Darlington configuration solved a problem with bi-polar transistors at the cost of a lot of problems – still there are times (think audio amps – analog applications) where it works just fine.

    1. Quote: “There is an attraction to avoid the base input resistor”

      I have some of these. The spec sheet calls them “Digital” FETs and they are specificity designed to be directly driven from TTL.

  36. Heeeelllllllloooo. This is a hacking site not a engineering one. Things here have to be built the way it is not supposed to, and most important with the resources available.”TIP” them up.

  37. throw away perfectly good part?! Blasphemy!

    I cant count the number of flatscreen’s, coffee makers, VCR’s, radios and game consoles i’ve disassembled for used parts. what i can count is how much i’ve spent on NEW parts over the years.

    ’bout $65.

  38. I just find it ironic that the main defense against this article circulating around (and being accepted) on the Arduino forms is that the old parts “get the job done” when that’s often the first go-to defense for Arduino. That Arduino users fend off criticism by stating that Arduinos get the job done, but then play off this article warning against parts that still “get the job done” seems a bit hypocritical, but maybe I’m over-generalizing a bit.

  39. that reminds me of a joke i made up 20-odd years ago in college. When I described someone as “a bit bipolar”, they said: Is that bad? “not if you’re a MOSFET” was my reply. I laughed.

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