Need help with LT spice op amp connections
My input signal is 0.7 volts and the amp amplifies by a factor of 10.
I decide the output signal by 10 and then feed it to inverting end of op amp
and the original signal at non inverting end of op amp.
I want to get difference between the 2 signals but i am getting a square wave as op amp seems to be running in high gain.
How can i set this op amp to unity gain so i get only the difference of 2 signals
View image: testamp
You can't do it as you have shown. The opamp will give a squarewave because the difference between the the two signals is huge (in opamp terms... even if it were only a fraction of a millivolt difference)
I'd have to think about how you would do it... something like an adjustable gain amp differential amp.
Have a look at fig 3 here for ideas. You might need more than one opamp to match and process the signals first.
High_Voltage_Diffamp: Analog Dialogue: Analog Devices
I ended up using 3 op amps
Thank you Mooly
Well done, its not an easy problem to crack :)
if you just want the diff measurement then you should look at waveform math - in the waveform viewer you can enter equations for trace definitions, multiply, divide, add, subtract any of the node voltages or terminal currents
if you want even more calculating power you can use B sources which create waveforms in the sim that are defined by equations
or look over a sim that is only BV equations and .func
Will need look more into the B sources
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