[sdiy] OTA as Voltage Controlled Resistor

[Donald Tillman]

On Apr 24, 2013, at 12:33 PM, Justin Owen <juzowen at gmail.com> wrote:

> 1) Can the double-ended circuit be used to replace a standard discrete resistor - i.e. is either 'end' replacing a leg/pin of a resistor?

Roughly, to a first approximation, yes.


> 2) Assuming the answer to #1 is 'yes' - has anyone got any idea of what sort of resistance range could be pulled from an OTA?  

The inverse of the transconductance (1/gm) which is set by the amplifier bias current, and include the effects of linearizing diodes and other resistance in the circuit.


> 3) Can someone provide examples of how a single-ended circuit might be used?

The single-ended circuit simply requires that one lead of the target resistor is grounded.


> In short, I'm wondering if an OTA VCR might be a suitable replacement for a vactrol under certain circumstances.

Yes, but... it wouldn't have the quirks that make the vactrol circuit charming, replacing them with these new OTA quirks.

  -- Don

--
Don Tillman
Palo Alto, California
don at till.com
http://www.till.com