SV: [sdiy] QVCO schemo up

[Ian Fritz]

At 03:53 PM 11/11/05, Harry Bissell Jr wrote:
>Using  the linearizing diodes ~guarantees~
>that you will have big offset troubles. The simulation
>can be trimmed easily to remove them.

I wouldn't say "guarantees".  It can happen if the input transistors are 
well matched but the diodes are not.  Makes selecting really good devices 
pretty difficult, though.   When I was working on discrete OTAs I found 
that each pair has to be matched to better than 50 uV.  Then the offsets 
are small and can be trimmed out and the the bias dependence can be quite 
small.  A good idea to use selected 3280's.

   Ian