In this note, we are going to learn about a topic called “What is Multistage Amplifier?” and also about its features. Welcome to Poly Notes Hub, a leading destination for engineering notes for diploma and degree engineering students.
Author Name: Arun Paul.
What is Multistage Amplifier?
A transistor circuit containing more than one stage of amplification is known as Multistage Transistor Amplifier.
In a multistage amplifier, a number of single amplifiers are connected in a cascade arrangement, with the output of the first stage connected to the input of the second stage via an appropriate coupling device, and so on. The purpose of the coupling device is –
- to transfer the alternating current output of one stage to the input of the following stage.
- and to separate the direct current circumstances of one stage from the next.
Figure depicts the block diagram of a three-stage amplifier. Each stage comprises of one transistor and its related circuitry, which is linked to the next stage via a coupling device.
The name of the amplifier is usually given after the type of coupling used. e.g.
| Name of Coupling | Name of Multistage Amplifier |
|---|---|
| 1. RC Coupling | RC Coupled Amplifier |
| 2. Transformer Coupling | Transformer Coupled Amplifier |
| 3. Direct Coupling | Direct Coupled Amplifier |
Features of Multistage Amplifier
Here are the features of each multistage amplifier –
- RC Coupled Amplifier: In RC coupling, a capacitor serves as the coupling device. The capacitor connects the output of one stage to the input of the next stage, allowing the a.c. signal in while blocking the d.c. bias voltages.
- Transformer Coupled Amplifier: In transformer coupling, a transformer serves as the coupling device. The transformer coupling performs the same two purposes, but also allows for impedance matching.
- Direct Coupled Amplifier: Direct coupling, also known as d.c. coupling, occurs when the individual amplifier stage bias conditions are constructed in such a way that the two stages can be connected directly without the need for direct current isolation.