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From: firstname.lastname@example.org (Gibbo)
Date: 04 Dec 2002 12:00:55 GMT
Organization: AOL, http://www.aol.co.uk
Subject: Re: CMMR op amp outside voltage rails ?
"fred bartoli" wrote:
>Gibbo a écrit dans le message :
>> I have simulated and breadboarded (they almost agreed !) an amplifier that
>> 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
>> 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.
>> as the differential amp, and one for the gain There has to be a less
>> complicated way.
>> I bet there's a single package that will do it all ?
>Chris, you didn't tell about the needed input impedance.
>What is your requirements ?
>If you can live with 100Kohm order BB-Ti has some difference amplifier with
>high common mode range. Look at INA146/148.
>The 146 is probably the one you want.
Thanks. I'll look them up but as I said in another post I'm dubious of BB and
their sudden discontinuations of supply. I forgot to mention required input
impedance as it's really not an issue so it wasn't in my mind. The source
impedance is less than 1 ohm. A current shunt.
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