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If I hook up a 25v-rated operational amplifier in a differential configuration, with a +/- 2.5v (5v) supply, can I measure signals 100 volts above the negative supply, so long as the difference between the two inputs is within it's rating?

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  • \$\begingroup\$ What specific diff-amp are you looking at? Can you draw as a schematic of your intended structure around the amp? \$\endgroup\$ – user2943160 Nov 30 '19 at 23:47
  • \$\begingroup\$ @user2943160 I don't have an exact structure in mind, I just want to know what the voltage rating of an amplifier really means in the differential configuration. \$\endgroup\$ – Hackstaar Dec 1 '19 at 0:03
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    \$\begingroup\$ Read the datasheet, see the absolute maximum limits and recommended operating conditions, do the circuit analysis to ensure that you remain within those limits based on your Vcc/Vee setup. You'll probably need a fairly high impedance from your +100V signal to your amplifier. \$\endgroup\$ – user2943160 Dec 1 '19 at 0:08
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    \$\begingroup\$ The number you are looking for is called the "common mode voltage". In general, you will not be able to use inputs outside your power supply voltage range. \$\endgroup\$ – WhatRoughBeast Dec 1 '19 at 0:09
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As long as the input common mode voltage rating is not exceeded, you can do that.

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, can I measure signals 100 volts above the negative supply?

Never directly. But you can attenuate /25 and bias to stay inside the IC’s specs with gain of 25.

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