2025 Component Abuse Challenge: A Transistor As A Voltage Reference
For our 2025 Component Abuse Challenge there have been a set of entries which merely use a component for a purpose it wasn’t quite intended, and another which push misuse of a part into definite abuse territory, which damages or fundamentally changes it. [Ken Yap]’s use of a transistor base-emitter junction as a voltage reference certainly fits into the latter category.
If you forward bias a base-emitter junction, it will behave as a diode, which could be used as a roughly 0.7 volt reference. But this project is far more fun than that, because it runs the junctions in reverse biased breakdown mode. Using one of those cheap grab bags of transistor seconds, he finds that devices of the same type maintain the same voltage, which for the NPN devices he has works out at 9.5 volts and the PNP at 6.5. We’re told it damages their operation as transistors, but with a grab bag, that’s not quite the issue.
We’ve got a few days left before the end of the contest, and we’re sure you can think of something worth entering. Why not give it a go!
