I'm tring to use a OP-AMP LM358P as a differential amplifier.
The circuit I'm using is like below; enter image description here

According to what I've study and expectations of SPICS, the out-put should be about 2.5(V1-V2). To be specific, I would V1, v2 will be 0~3.3V and the expected output is proportional -8V~+8V. However, the actual circuit provides constant V which is the same with Vcc voltage; actually bit less than the Vcc when I tried with 12V and 24V as Vcc.

So, what could be the possible cause that makes the circuit does not work as expected?


1 Answer 1


You have the + and - input swapped (positive feedback, rather than negative) so it will snap to as close as it can get to either rail, depending on the inputs.


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