On 2013-05-01, Fons Adriaensen wrote:
The diode is not 'perfect', it will have some voltage drop depending on the current flowing in it. The result may well be 'desirable', i.e. in practice better than what would be obtained by using a 'perfect' diode.
Perhaps the nastiest commonly used example of this I know of is biasing diodes (often using negative feedback to keep them there) right into the middle of the knee region where they're starting conduct. There the voltage-current-characteristic is locally exponential, so that you can derive logarithms and exponentials in the analog domain when you linearly amplify the local behavior. Then you can do analog computer things like multiplication via accumulation on the resulting voltages, and convert back.
There's about a million things which can go wrong with this kind of an unstable setup. And it does. And then some people like it and build entire circuit topologies to amplify the "defect" into a unique, sellable product. If you want to emulate something like that, you can't just look at the circuit board, because there you'd be like o_O, WTF?!? Seriously, analog engineers do the weirdest things, some of which might not even be described in the diagrams e.g. for trade secret reasons. (I for example know of an analog synth whose secret still appears to be safe, because it has to do with intentional parasitics from a nearby coil, never put in the patent diagram.)
In this vein the starting point prolly would be the Moog ladder, in its nonlinear region. It's hideously complex for such a charming little thing.
-- Sampo Syreeni, aka decoy - de...@iki.fi, http://decoy.iki.fi/front +358-50-5756111, 025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2 _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
