I'm having difficulty finding input resistance because for some reason there is no virtual ground across the inputs, so the current flowing through each is not the same. What am I doing wrong?
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VCC and VEE were 15V and -15V originally, as can be seen by my previous post above. But I don't really see how the output is any way related to input resistance.Hi geft,
it would be wise to reduce the gain or the input voltage - or to increase the power supply voltages.
Why?
Because with 1 Volt input signal and a gain of (1+14)=15 you operate the device outside of its linear amplification range.
Does that mean I should just short the feedback loop and remove R1? Or short both inputs together?The opamp will drive the negative input to a virtual ground. If you then connect a DC source to the other end of R1. What will the current in R1 be then
What do you mean? Which one should I be looking for?In opamp circuits. The input impedance for the system, do not have to be the same as the opamp input impedance.
Thanks, but why does it work and mine doesn't? Shouldn't an op-amp work with DC as well?Try to use AC sweep analysis. And Rin = Vin/Iin = 1Meg.
Sorry, I thought virtual ground only exists in op-amp circuits with feedback, so I assumed it's a given. The picture is something I took from Google to illustrate input resistance...Geft, in post#8 you have no feedback - in contrast to your circuit in post#1.
Ah, now I see what you meant. I didn't know this before. Does that mean 16V voltage rails will be sufficient?In case of feedback it is important - as I have mentioned before - that the output is not in saturation.