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OP1177 Common Mode Voltage

Question asked by zi2012 on May 21, 2013
Latest reply on May 30, 2013 by NeilJ

I am trying to use the OP1177 as a differential amplifier to measure a DC current shunt. It will have a gain of 50, 2k and 100K ohm. Most of the time the op1177 will be reading the shunt from the low side. It also needs to be able to read a high side shunt. The high side maximum is 200Vdc. The data sheet doesn't specify the CMV, probably due to the reliance on the external resisters. The only paths for the CMV are the Rg resister to ground and opamp output via the Rf resister. I don't think the CMV will be a problem due to the fact that the opamp is powered by an isolated power supply. The common Rg is attached to the isolated power supply return.  So there is no current path between the input CMV and ground/common. Can the OP1177 withstand +-200vdc without a current path?

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