[sdiy] discrete circuit question:

[Ken Stone]

Totally useless. All it does is keep the load on the input the same whether
the input is positive (via transistor) or negative (via diode), less the
1.2V gap around 0V where there is no load. It looks like whoever drew this
was either making errors in their reverse engineering, or was of the "lets
stick this there and see what happens" mentality.

I would suggest that if anything, the diode was meant to go to the
collector, not the emitter, and the other end of the associated resistor
directly to the base, in which case it would be providing a very crude form
of biasing to the transistor.

Ken

>Please take a look at this circuit:
>
>http://forum.musikding.de/attachements/Trem.gif
>
>(It's from the guts of a single transistor chopper style tremol circuit).
>
>What role does the diode and the series resistor play? My guess is, that 
>the diode protects the basis-emitter junction of the tranny in case 
>there is a large signal swing that could possible permanently damage the 
>BE-junction   If so - why the series resistor? I doubt the leakage 
>current of the diode would make any difference at all, so in my oppinion 
>the resistor is useless.
>
>I have a discussion about that little detail on a guitar fx forum, and 
>we're a bit stuck, so I thought I'd rather ask here.
>
>Thanks,
>  Nils
>
>
>
>
>
_______________________________________________________________________
Ken Stone   sasami at hotkey.net.au or sasami at cgs.synth.net
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