[sdiy] Replacing CA3080 with CA3046 ??

[Scott Gravenhorst]

karl dalen <dalenkarl at yahoo.se> wrote:
>
>--- Antti Huovilainen <ajhuovil at cc.hut.fi> wrote:
>> On Sat, 9 Apr 2005, Tim Parkhurst wrote:
>> 
>> > http://www.idg.se/personal/bergfors/bergfotron/VCA.htm
>> > This comparison shows that actually the lowly 13600 makes a pretty darn
>> good
>> > VCA. This list includes the 3080 , the SSM2024, 3046 and 3086-based OTAs,
>> > amongst others. It doesn't include the 3280 or 5517 however.
>> 
>> What is the reason for the higher offset of the LM13600 circuits compared 
>> to CA3080?
>> 
>> Antti - Who will need some 40 VCAs for one project...
>
>The thing with the 13600 and 700 is that the offset is not constant,
>it responds in a somewhat eliptical fashion depending on varying Iabc,
>from some 500uV to 25mV and back, i tested this long time ago about
>12-15 13700 they all shows this in varying amount. Used the classic PNP 
>Iabc source expo.

That's interesting.  Is there an active method to compensate, like using one
OTA with 0 volts on it's inputs, but varying it's Iabc the same as another OTA
to generate a correction voltage to cancel the offset?  

Or would this be useful only if the other OTA is part of the same package as
the compensator?



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