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https://www.circuitlab.com/circuit/vwayc4/difference-amplifier/ I want to plot the 2 dc inputs and the dc output voltages from this 741 difference op amp circuit. Please advise how to set up the plot in the simulation. I am a novice in electronics so please explain setup clearly. Many Thanks Michael

Your DC Solver simulation is OK. The reason V(V2) doesn't plot is just because your V2 label is not on the pin of V2. Move it up 1 grid square until you see the join dot appear.

Your Time Domain simulation may not give sensible results because you need a time step of > 0.01 * (stop time)

See:

https://www.circuitlab.com/docs/

and

https://www.circuitlab.com/circuit/nu8w4b/

for more about how to set up sweep parameters

and

https://www.circuitlab.com/circuit/d4qjc5/relaxation-osc-fixed-01/

for more on choosing time steps.

Thanks Just one other question. This is a difference circuit but the output is greater than i expected. Two Inputs of -2.5vand 3.6v gives an output of 9.692V. I think it should be 6.1V Please advise

Think of the circuit as two amplifiers.

One is the inverting amp. The other is the non-inverting amp.

An inverting amp has a gain of

Vout/Vin = -Rf/R2

where Vin is the voltage at the input end of R2.

Hence your opamp has a non-inverting gain of:

-100k/100k = -1

A non-inverting amp has a gain of

Vout/Vp = (1+Rf/R2)

where Vp is the voltage at the non-inverting input pin of the opamp.

Hence your opamp has a non-inverting gain of:

1+100k/100k = +2

You need to connect another 100k resistor from the non-inverting input of the opamp to ground to attenuate V1 by a factor of 2 to give an overall non-inverting gain of +1.

More:

Google:

opamp difference circuit

Thanks very much for a very clear explanation. Michael