We have covered enough of the work of [Ken Shirriff] on these pages to know that when he publishes something, it will be a fascinating read and work of the highest quality. And so it is with his latest, a very unusual op-amp on which he performs his usual reverse engineering. Not only does it lead us directly to some of the seminal figures in the early years of the semiconductor industry, it turns out to have been a component manufactured to a NASA specification and of which there is an example on the Moon.
The metal can revealed a hybrid circuit when the lid was removed, one in which individual transistors were wired together with a single block containing a group of thin-film resistors. At the start of the 1960s the height of consumer electronics would have been your domestic TV which would have been an all-tube affair, so while it sounds archaic this would truly have been a space-age piece of technology. The designer is revealed as the legendary [Bob Pease], and the transistors take us back to the semiconductor physicist [Jean Hoerni], inventor of the planar transistor and one of the famous eight defectors from Shockley Semiconductor in the 1950s who kick-started the semiconductor boom.
The op-amp itself is a relatively simple design without the compensation capacitor you might expect in a modern device, but what makes it unusual for its time is the use of [Hoerni]’s planar JFETs at its input. [Ken]’s analysis is as usual extremely thorough, and the bit of Silicon Valley history it gives us is the icing on the cake.
If you have a thirst for ancient op-amps, you might like our look at the first commercially available fully-integrated design, the Fairchild μA702.
Deep in the heart of your latest project lies a little silicon brain. Much like the brain inside your own bone-plated noggin, your microcontroller needs protection from the outside world from time to time. When it comes to isolating your microcontroller’s sensitive little pins from high voltages, ground loops, or general noise, nothing beats an optocoupler. And while simple on-off control of a device through an optocoupler can be as simple as hooking up an LED, they are not perfect digital devices.
But first a step back. What is an optocoupler anyway? The prototype is an LED and a light-sensitive transistor stuck together in a lightproof case. But there are many choices for the receiver side: photodiodes, BJT phototransistors, MOSFETs, photo-triacs, photo-Darlingtons, and more.
So while implementation details vary, the crux is that your microcontroller turns on an LED, and it’s the light from that LED that activates the other side of the circuit. The only connection between the LED side and the transistor side is non-electrical — light across a small gap — and that provides the rock-solid, one-way isolation.
Continue reading “Optocouplers: Defending Your Microcontroller, MIDI, And A Hot Tip For Speed”
No circuit is so trivial that it’s not worth thinking hard about. [Charles Wilkinson] wanted to drive a solenoid air valve that will stay open for long periods of time. This means reducing the holding current to prevent wasting so much power. He stumbled on this article that covers one approach in a ridiculous amount of depth.
[Charles] made two videos about it, one where he debugs the circuit and learns things live on camera, and another where he sums it all up. We’ll be walking you through the long one, but feel free to skip around.
Continue reading “Overthinking Solenoid Control”
We have lost something in PCB design over the last few decades. If you open up a piece of electronics from the 1960s you’ll see why. A PCB from that era is a thing of beauty, an organic mass of curving traces, an expression of the engineer’s art hand-crafted in black crêpe paper tape on transparent acetate. Now by comparison a PCB is a functional drawing of precise angles and parallel lines created in a CAD package, and though those of us who made PCBs in both eras welcome the ease of software design wholeheartedly we have to admit; PCBs just ain’t pretty any more.
It doesn’t have to be that way though. Notable among the rebels are Boldport, whose latest board, a tribute to the late linear IC design legend [Bob Pease], slipped out this month. They use their own PCBmodE design software to create beautiful boards as works of art with the flowing lines you’d expect from a PCB created the old-fashioned way.
The board itself is an update to an earlier Boldport design, and features Pease’s LM331 voltage to frequency converter IC converting light intensity to frequency and flashing an LED. It’s one of the application circuits from the datasheet with a little extra to drive the LED. Best of all the kit is a piece of open-source hardware, so you can find all its resources on GitHub.
We are fans of Boldport’s work here at Hackaday, and it should come as no surprise that we have featured them before. From one of their other kits through several different pieces of PCB wall art, to their work making an appearance in Marie Claire magazine they have graced these pages several times, and we hope this latest board will be one of many more.
We are saddened by the recent passing of [Bob Pease]. You may not be familiar with the man, but his work has touched your lives in more ways than you can count. As an electronics engineer who specialized in analog components he was responsible for hardware that made some of the electronics in your life possible, and designed components that you’ve probably used if you dabble in electronic design.
EDN has a lengthy obituary celebrating his life and accomplishments. [Bob] was part of the 1961 graduating class at MIT. He started his career designing tube amplifiers before finding his way to a position at National Semiconductor about fifteen years later. Throughout his career he worked to promote education about analog electronics both through written text, and more recently as the host of Analog by Design, an online video program where a panel of experts discuss the ins and outs of electronics.
[Bob] was killed in an automobile accident on June 18th at the age of 70.