The following section explains operation al Amplifier in details.
- An operational amplifier is a direct coupled high gain amplifier consisting of one or more differential (OPAMP) amplifiers and followed by a level translator and an output stage.
- An operational amplifier is available as a single integrated circuit package.
- The block diagram of OPAMP is shown in fig1.1
- The input stage is a dual input balanced output differential amplifier.
- This stage provides most of the voltage gain of the amplifier and also establishes the input resistance of the OPAMP.
- The intermediate stage of OPAMP is another differential amplifier which is driven by the output of the first stage.
- This is usually dual input unbalanced output.
- Because direct coupling is used, the dc voltage level at the output of intermediate stage is well above ground potential.
- Therefore level shifting circuit is used to shift the dc level at the output downward to zero with respect to ground.
- The output stage is generally a push pull complementary amplifier.
- The output stage increases the output voltage swing and raises the current supplying capability of the OPAMP. It also provides low output resistance.