Hello,
I'm using an opamp as a differential amplifier. I have trouble figuring out the problem. So i need your help.I have attached the circuit- Fig 1. The gain is 100. V1 is supplied from a potentiometer which is 0V to 10V. I want the V2 to detect the voltage output from a transistor source pin.
I have kept the gate voltage at 0V. So the transistor is OFF and no voltage should be present at the SOURCE pin.
But when i change the V1 voltage (non inverting input) from 0V to 10V, i see the same voltage 0V to 10V at the source pin eventhough the transistor is OFF. I checked to see whether the transistor is bad but it is fine. I verified it with a diode (Fig 2) between SOURCE pin of the transistor and V2. Now i tested it again with 0V to 10V at V1. I did not see any voltage at source pin of the transistor. But i do see same voltage (0V to 10V) at V2.
I dont understand why there is 0V to 10V at V2 when it should read only 0V from Source pin of the transistor. Could someone please help me.
Thanks,
RP
I'm using an opamp as a differential amplifier. I have trouble figuring out the problem. So i need your help.I have attached the circuit- Fig 1. The gain is 100. V1 is supplied from a potentiometer which is 0V to 10V. I want the V2 to detect the voltage output from a transistor source pin.
I have kept the gate voltage at 0V. So the transistor is OFF and no voltage should be present at the SOURCE pin.
But when i change the V1 voltage (non inverting input) from 0V to 10V, i see the same voltage 0V to 10V at the source pin eventhough the transistor is OFF. I checked to see whether the transistor is bad but it is fine. I verified it with a diode (Fig 2) between SOURCE pin of the transistor and V2. Now i tested it again with 0V to 10V at V1. I did not see any voltage at source pin of the transistor. But i do see same voltage (0V to 10V) at V2.
I dont understand why there is 0V to 10V at V2 when it should read only 0V from Source pin of the transistor. Could someone please help me.
Thanks,
RP
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