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Subject: Re: CMMR op amp outside voltage rails ?
X-Newsreader: Forte Agent 1.92/32.572
Date: Tue, 03 Dec 2002 20:50:55 -0500
NNTP-Posting-Date: Tue, 03 Dec 2002 20:51:03 EST
Organization: Bell Sympatico
That's very much the configuration I have used . For best offset
accuracy I recommend switching the gain resistor and the resistor on
the opposite port.
Also, since you probably have a spare opamp (4) Why don't you divide
the gain switching between the last two ?
You will have to get better supply voltages. If you have a clock
signal you may generate all the required voltages from it. Positive
and negative. If you only have a + voltage make an oscillator and
rectify the voltage
On 04 Dec 2002 00:30:40 GMT, firstname.lastname@example.org (Gibbo) wrote:
>I have simulated and breadboarded (they almost agreed !) an amplifier that we
>need with the following specs:-
>Differential voltage input of -60mV to +60mV
>This could be sitting on an offset between -5 volts to +50 volts
>Available power supply is a single rail 5 or 6v (not yet decided)
>Gain of 50 and 500 (switchable)
>Bandwidth DC to 1KHz
>Gain accurancy better than 1%.
>Offset accuracy less than 0.05 volts on the output.
>Temperature/time drift of offset is not such an issue as the micro periodically
>calibrates for this. Though of course it would be nice to remove this
>My solution uses 3 op amps. One of them to remove the offset on the input. One
>as the differential amp, and one for the gain There has to be a less
>I bet there's a single package that will do it all ?
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