Hello Inter web
I am confused with virtual ground used for op amps and I cannot verify my calculations with measurment because of virtual ground.
My setup is as follows: LM358 connected in a non inverting amplifier configuration with a gain of 100. The power supply going to the op amp is 9v to the possitive power rail and -3v to the negative rail.
The input signal is 20mV. This signal is generated by running a variable current through a known resistor. The output should be 2v. I measure the signal relative to 0v but I am confused as to what ground the op amp see's the signal relative to? 0v or -3v?
If I measure the voltage drop over the known resistor I measure 20mV. When I measure the signal that goes into the op amp what ground do I put my negative tester lead to? -3v or 0v?