3080 VCA

[POLARIS at VAX1.Mankato.MSUS.EDU]

Hi all,

I had a look at data for the 3280AE (which is dual), and with linearization
diodes beeing used, may be a better chip than the 3080.  Note that there
are two version of the 3280, one having tighter specs.  The 3280AE seems
to have a lower offset than the 3080.  Is it not the offset which causes the
thumpiness of a vca, or are there other factors?  I made a 3080 VCA from
an EN design, and after carefully minimizing offset, there was no thump
even with short attacks.  I guess the 3280AE would be even better in this
regard?  Also, RE: noise,  maybe this chip would be better in this regard as
well, because I think it can accept larger dif. input swings (with the
linearization diodes working) than the 3080.  As far as using current
sources, the EN circuit has a clever way of handling this by putting the
OTA current pin and neg supply pin in the feedback loop of an op-amp.
Very simple and seems to work well.

A URL you can use to get at this info (in PDF format) is:

http://eser.postech.ac.kr/data/harris/lin-tel.html

There are specs for the 3280 and 3280A (which are slightly better, more $$)



Dave