Figure Shows the Basic Block Diagram of OP-AMP
An OPAMP is a Multistage Amplifier with High Input Impedence and Low output Impedence
The basic block diagram constitutes mainly four stages
1. Input stage
2. Intermediate Stage
3. level Shifting stage
4. Output Stage
The Input Stage
The input stage consisting of "Dual Input Balanced Output Differential Amplifier"
This stage Determines the Input Impedence of Operational Amplifier, having two inputs Inverting and NonInverting.
In this stage Differential amplifiers with a constant current source is used inorder to Increase the CMRR (common mode rejection ratio).
The Intermediate Stage
This stage also posses Two inputs but having only One Output. It is usually another Differential amplifier, which is driven by the preceding Output.
This stage is commonly used to Increase the gain of amplifier. In the quiescent condition some dc error voltage may appears on the Output of This stage.
The Level Shifting stage
This stage is usually an Emitter Follower circuit in order to shift the error dc Level of preceding stage.
This stage eliminate the chance of signal distortions.
The Output Stage
It is final Stage of an Operational amplifier, it is usually a complementary symmetry push pull Amplifier.
This Stage Increases the Output voltage swing and the current delivering capabilities.
It also essential for providing low output Impedence.
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