Problem with OpAmp Simulation in LTspice

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mechguy

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Hello,

Recently I have some problem with simulation in LTspice for operational amplifier (inverting amplifier) circuit. The source voltage and first resistance before opamp is 9 V and 3.6m ohm. The second resistance is 1k ohm. So, the expected output voltage should be

Vout = 9 / 3.6m* 1000 = 2.50 V

But instead, it shows the value of 1.21 V after running the simulation.

I have attached my LTspice drawing here. Kindly appreciate any help and suggestion to me. Thanks in advance! ;-)
 

I have three recommendations:
* Check your gain formula
* Realize that 3.6m means 3.6 milliohms
* Become familiar with problems of single supply (or use double supply)
 

This gain formula makes more sense for an inverting amplifier

Vout = -(9 / 3600* 1000) = -2.50 V

You'll notice that neither 3.6m nor 3.6Meg are correct, also the expected output voltage is negative, which leads to the dual supply point addressed by LvW.
 

In my view it shoud be 3.6K i.e. kilo-ohm for the formula that you said .....as FvM pointed out your OPAMP is working in Non-inverting mode thus the O/P should be negative.....

Good Luck
 

What you got as Vout = 1.21V is the lower saturation voltage of LT1001 for an ouput load of 1K connected to 9V (since Vin- voltage is close to 9V due to the 3.6 milliOhm).
 

Finally, my problem is solved:
1. It's my carelessness for the equation, yes it's 3.6k.
2. I've changed my voltage supply inversely.
3. I apply double voltage supply to OpAmp.

The output voltage is + 2.5V. Thanks for your helps!
 

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