We always enjoy [w2aew’s] videos, and his latest on zener diodes is no exception. In it, he asserts that all Zener diodes are not created equal. Why? You’ll have to watch the video below to find out.
Zener diodes are one of those strange items that have several uses but are not as popular as they once were. There was a time when the Zener was a reasonable way to regulate a voltage inexpensively and easily. Unfortunately the regulation characteristics were not very good, and the power lost was very high. But that was sometimes a reasonable trade, compared to putting a pass transistor and the associated discrete circuitry in place to make a linear regulator. With the advent of chips like the 7800-series regulators, you can have a high-quality regulator with one extra wire and still keep your costs under $1. Even if you want to do better and go with a switching power supply, that’s easy now and not much more expensive.
So you don’t see as many Zener power supplies as you used to. But there are still cases where they are useful. For example as part of a voltage reference circuit, since they can be reasonably accurate if the load current is constant. They are also useful for clipping voltages, circuit protection, and can even be part of a random number generator that will take advantage of their inherent noise during avalanche operation.