[sdiy] expo accuracy? or integrator accuracy?, or both?

[René Schmitz]

At 15:32 07.02.03 +0100, you wrote:
>Not really. CA3140 has a zener diode ESD protection network.
>Without that you would most probably destroy the input
>very soon. This means leakage, I have measured 30-40pA
>at room temperature.

The CA3140 hasn't enough slewrate IMO. (Togehther with a fast 
discharge this leads to overshooting behaviour, because the 
integrator can't properly follow on the reset.)

>OTOH: the OPA111 (or so) is JFET, but has very low leakage
>and good gain /bandwidth as Ian Fritz pointed out...

Still I wouldn't bother with that, as long as you use a jFET 
as your discharge switch which has a leakage in the order of 
100pA.

I think it is futile to concentrate on a few aspects of VCO design. 
You always will have to look at the whole picture so to speak.

Cheers,
 René


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uzs159 at uni-bonn.de
http://www.uni-bonn.de/~uzs159