Cursed Circuits: The Reverse Avalanche Oscillator That Defies Logic
Cursed circuits #6: reverse avalanche oscillator
I explore a baffling oscillator circuit that uses an upside-down NPN transistor with a floating base. Despite looking broken, it works by exploiting avalanche breakdown at surprisingly low voltages. This quirky setup creates a unique negative resistance effect, causing a capacitor to charge and discharge in a loop that mimics old neon lamp oscillators. It is an inefficient but fascinating reminder of how complex semiconductor physics can be.
But sometimes, bad rises to an art form.
- voidUpdate
You can even use it to make a simple audio synth: https://www.lookmumnocomputer.com/simplest-oscillator
- cryo32
This isn't particularly cursed. I mean we've had avalanche pulse generators for well over half a century easily. It's just exploiting semiconductor characteristics they don't teach you in the usual garbage undergrad textbooks.
- pseudohadamard
> "It’s hard to build an oscillator"
I would beg to differ. It's hard to not build an oscillator. An awful lot of digital design is avoiding building oscillators all over the place.
Incidentally, the coolest anti-oscillator I've seen used the back EMF from a relay to push a transistor past its breakdown voltage, and that was the oscillating element.