stabilizing a germanium transistor with a reverse-biased germanium diode

[mordechai]

The Rangemaster clone on Fuzz Central uses a reverse-biased germanium diode (1n34a) to help the germanium transistor improve its temperature stability by running the diode between the base and the emitter of the transistor.  Is this advisable for fuzz face circuits too?  What would be the drawbacks to doing this?

[rutabaga bob]

Look at the 'toneblaster mk 2.5' thread...

[pinkjimiphoton]

no drawbacks.

the idea is to help with temp stability.

the ge diode and transistor are both gonna leak;

by  opposing them, they compensate for each other's leakage. great trick, works wonders in a fuzz face and has zero to minimal effect on tone.

ONLY works with germanium transistors. it came from the old obsolete plate to plate site, and the "britface" article.

[R.G.]

What you're trying to do is have the reversed diode suck as much leakage out of the base as the collector base leaks, and to have it track the C-B over temperature.

This works best if you match the C-B and the reversed diode for leakage at a common temperature. If the diode is dramatically more or less leakage than the C-B, it over- or under-compensates.

[pinkjimiphoton]

thanks for the clarification, RG

i really gotta upload the old plate to plate article. one of these days, i'll update my dot com with a bunch of lost stuff.