Question

How ope amp works?

Answer 1

The basic operational amplifier has 2 signal inputs and one signal output. It also has two power supply inputs - generally of opposite polarity eg:+/- 15 volts. The inputs to an op-amp are marked + and - for non-inverting and inverting input respectively. If the voltage at the non-inverting input exceeds the voltage of the inverting input the output voltage goes positive as high as it possibly can. If the voltage of the inverting input exceeds the voltage of the non-inverting input the output voltage goes as negative as it possibly can. The resistor network around a basic op-amp circuit is designed to keep both inputs at the same voltage for an output voltage somewhere between the positive and negative saturation voltages.

Answer 2

This means the output voltage is limited to the some values?

Answer 3

Yes - the voltages around the resistor network are divided in such a way as to make the voltage at the inverting input nearly the same as the voltage at the non-inverting input. If the inverting voltage is less, the output voltage continues to rise until the voltages are equal. If the inverting voltage is a little greater, the output voltage will fall until the two input voltages are equal.

You asked a very general question. So, I tried to give you a very general answer.