Problem with Op-Amp differential amplifier

[imanjohn]

Hello,

I have implemented a simple differential amplifier with an OP07 IC. R4 = R3 = 47K, R1 = R2 = 2K.

When I connect inputs (V1 and V2) so that the voltage difference be 0 at the inputs, I always see 1.5V on output. When I apply small differences at the input, the output does not vary and it is 1.5V. I did not do anything for offset nulling and I checked on several ICs. Would you please let me know the problem?

 

[LvW]

When I connect inputs (V1 and V2)

Just connect or connect both to ground?

 

[imanjohn]

Just connect or connect both to ground?

Just connect! But I will check with GND and voltage applied.

If I connect both inputs to the GND, the output will be 7V (the V+ is 10V and V- is GND).

If I connect inputs to 2V, then the output remains 1.5V.

 

[LvW]

If I connect both inputs to the GND, the output will be 7V (the V+ is 10V and V- is GND).

So you work with single supply ?
Do you know about the restrictions for single supply (proper biasing)?

 

[imanjohn]

So you work with single supply ?
Do you know about the restrictions for single supply (proper biasing)?

Yes, I do. I want to have a simple subtractor to make a current limiter.

Unfortunately I don't know anything about proper biasing for single-supply op-amp circuits. Could you please introduce some text to refer? Do you have any idea to solve the problem?

Thank you very much.