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
   (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

Also I'd use a 13600 or 3280 instead of the 3080 for the obvious noise

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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