At 02:49 AM 4/22/2012, Forrest Christian wrote:
>I'm currently using an INA196 high side shunt amplifier in a couple of
>applications.   As I asked/discussed a couple of weeks ago, one of them
>involves current monitoring the currents through some P-channel FETS,
>and am looking at moving the sensing from a sense resistor to sensing
>across the FETS.
>
>I of course need to deal with the situation where the FET is off,
>producing a high differential voltage across the amplifier.

I've handled this in a couple of different fashions.

1) Just rely upon well-matched high-value series resistors to the=20
op-amp and add clamp diodes across the op-amp inputs.

2) Use another (small) FET who's gate is tied to the gate of the main=20
FET - use that small FET to disconnect the sense lead from the main=20
FET while it is turned off.

I've used both techniques successfully in the past.

dwayne

--=20
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

--=20
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