How Operational Amplifiers Work

An operational amplifier can be thought of as a simple box or block containing an amplifying device, such as a bipolar transistor, a field effect transistor, or an operational amplifier, which has two inputs and two outputs (grounded), the output signal being much larger than the input signal because it has been "amplified".

Operational amplifier has two power supply modes, dual power supply and single power supply. For an operation with dual power supply, the output value can be changed up or down at zero voltage, or the output can be set to zero at zero differential input voltage. For single-supply operation, the output value is only allowed to change within a certain range between the power supply and the ground.

For general Operational Amplifiers, the input potential is required to be in the range from a certain value above the negative power supply to a certain value below the positive power supply, but it can also be changed from a negative power supply to a positive power supply in the whole range after special design, even slightly higher or lower than the positive power supply. This kind of operation amplifier is called track-to-track input Operational Amplifier.

operational amplifier are generally considered to have the following characteristics:

1. Infinite open-loop gain G = V out / V in

2. The input impedance R in is infinite, so the input current is zero

3. Zero Input Misalignment Voltage

4. Infinite output voltage range

5. Infinite bandwidth with zero phase shift and infinite swing rate

6. Zero output impedance R out

7. Zero noise

8. Infinite common mode rejection ratio (CMRR)

9. Infinite power rejection ratio.