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will inverting op-amp work with no R1?

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uday mehta

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hi,
my senior have given me a circuit to make a pcb and test. I have made that. but I didn't understand the output as I think that some thing wrong in the circuit.
circuit consist of a mcp6022 opamp. apply 20mV ac, no R1, but Rf = 40 M ohm at inverting terminal.
non-inverting terminal is connected to ground.

my question is that without R1 will this circuit work. if yes then what will be the output voltage.
I have uploaded the circuit diagram.
 

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mrinalmani

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Without the input resistor R1, the OP AMP will not work as an amplifier. It will work as a square wave generator with frequency equal to the the frequency of the input signal. However if the impedance of the input signal is comparable to the feedback impedance, the circuit may become unstable and fail to oscillate. But in general, the source impedance should be much smaller than 40M ohm an the circuit should work.
 
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