OTA question
Don Tillman
don at till.com
Wed Oct 11 17:57:00 CET 1995
From: Haible_Juergen
Date: Wed, 11 Oct 95 15:14:00 PDT
Using a CA3080 plus a buffer opamp, there are
basically two possibillities to build VCA's or
VC-integrators:
(1) the OTA feeding a resistor/capacitor to gnd,
plus an opamp as unity gain buffer
(2) the ota feeding an inverter/inverting integrator
built of an opamp and a resistor/capacitor in it's
feedback loop.
If it were my design, I would do a variation of (1) with the OTA
feeding a capacitor/resistor to ground and buffer it with an FET
source follower. This will keep the circuit free of nasty opamp-style
feedback.
Also I'd use a 13600 or 3280 instead of the 3080 for the obvious noise
reasons.
And if you use the 3280, you get to decide whether you want to control
the gain, the attenuation, or some combination of the two, which
should provide for some variations in the character of the circuit.
-- Don
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