Cursed circuits #6: reverse avalanche oscillator
lcamtuf.substack.com
Cursed circuits #6: reverse avalanche oscillator
1–10 of 28 posts
Re: Cursed circuits #6: reverse avalanche oscillator
#2This 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.
Re: Cursed circuits #6: reverse avalanche oscillator
#3You can even use it to make a simple audio synth: https://www.lookmumnocomputer.com/simplest-oscillator
Re: Cursed circuits #6: reverse avalanche oscillator
#4Delightfully cursed.
I wonder how consistent the breakdown voltages are between manufacturers? I mean, I am sure there is some spec, but is it not just a minimum in this case?
Re: Cursed circuits #6: reverse avalanche oscillator
#5This 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.
> the usual garbage undergrad textbooks
Out of interest, please could you give some examples of textbooks you consider garbage, and some you consider not to be (undergrad or otherwise)?
Re: Cursed circuits #6: reverse avalanche oscillator
#6This 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.
> the usual garbage undergrad textbooks Out of interest, please could you give some examples of textbooks you consider garbage, and some you consider not to be (undergrad or otherwise)?
Garbage -> Sedra and Smith particularly - hate it, anything which kicks you in the nuts right up front with Laplace and networks abstractions, anything from Pearson - have never seen a good one.
Good -> Razavi (Fundamentals of Microelectronics), Art of Electronics, most Jim Williams stuff (AN's and articles), Bowick RF Circuit design. They're actually useful.
Re: Cursed circuits #6: reverse avalanche oscillator
#7You can even use it to make a simple audio synth: https://www.lookmumnocomputer.com/simplest-oscillator
The man is a treasure
Re: Cursed circuits #6: reverse avalanche oscillator
#8Earlier quoted context omitted.
> the usual garbage undergrad textbooks Out of interest, please could you give some examples of textbooks you consider garbage, and some you consider not to be (undergrad or otherwise)?
Garbage -> Sedra and Smith particularly - hate it, anything which kicks you in the nuts right up front with Laplace and networks abstractions, anything from Pearson - have never seen a good one. Good -> Razavi (Fundamentals of Microelectronics), Art of Electronics, most Jim Williams stuff (AN's and articles), Bowick RF Circuit design. They're actually useful.
I find Sedra/Smith a terrible introduction, but a good reference. It's nice once you've already built an intuition for how things work to be able to go back & build up the mathematical models, but trying to understand the behavior of circuits from the math first is a bad order.
Re: Cursed circuits #6: reverse avalanche oscillator
#9What would happen if you added a capacitor (to ground) on the base? Could you adjust the frequency?
Re: Cursed circuits #6: reverse avalanche oscillator
#10Delightfully cursed. I wonder how consistent the breakdown voltages are between manufacturers? I mean, I am sure there is some spec, but is it not just a minimum in this case?
It's one of those characteristics you can't rely on unless you select / bin parts. Also depends on temperature. Which is why no one does this in a production design - it's expensive and unreliable.