In this video, the multistage amplifier configuration of BJT is explained with an example. By watching this video, you will learn the following topics:
0:20 What is Multistage Amplifier? Why it is used?
1:26 Effect of Source and the Load Impedance on the Amplifier
6:51 Multistage Amplifier (The calculation of overall voltage gain)
10:19 Example
What is Multistage Amplifier? Why it is used?
Sometimes the single amplifier may not be able to provide sufficient gain for the specific gain. To obtain the required gain, the multiple amplifier stages need to be cascaded. Or sometimes for the impedance matching at the input or output side, one needs to use the multiple amplifier stages.
The Multistage amplifier is the cascade connection of such multiple amplifiers.
Each amplifier is coupled to the next amplifier using the coupling capacitor.
The coupling capacitor blocks the DC voltage and passes only the AC signal to the next stage.
Calculation of voltage gain of Multistage Amplifier:
In the multistage amplifier, each amplifier stage acts as a load to the previous stage.
So, the overall voltage gain depends on the input and output impedance of each stage.
In this video, how to calculate the voltage gain of the multistage amplifier is explained in detail with example.
Choice of Transistor Amplifier in Cascade Connection:
The source and the load resistance plays an important part in deciding the overall gain of the multistage amplifier.
When the input has high source resistance then for impedance matching the common collector (CC) amplifier is used as a first stage.
Similarly, to drive the low impedance load, the common collector is used as a buffer at the last stage.
But generally, it is not used as an intermediate stage (Because its voltage gain is less than unity)
As an intermediate stage, the Common Emitter amplifier is often used because of its high voltage gain.
At high frequency, the common base amplifier is used as a first stage for the impedance matching.
For more solved examples on BJT, check this playlist :
This video will be helpful to all the students of science and engineering in understanding the concept of a multistage amplifier.
#MultiStageAmplifier
#BJT
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