- In BJT configuration it requires two ports network namely input port and output port.
- The input port are require 2 input terminal and the output port require 2 output terminal therefore it requires 4 terminals due to it is called as 2-port, 4-terminal network.
- There is a common terminal for an input port and output port. Then there will be only 3 terminals instead of 4 terminals in this 2-port due to this is called a 2-port, 3 terminal network it shown fig below.
- The Bipolar junction transistor (BJT) has only three terminal namely an emitter, base and collector.
- When a transistor is to be connected in circuit like a 2-port, 4 terminals, it is not possible because it has only three terminals e.g. emitter, base and collector.
- This difficulty is overcome by treating one of the three terminals as a common terminal to input port and output port.
The types of BJT configuration:
There are three types namely;
- Common base (CB) configuration.
- Common emitter (CE) configuration .
- Common collector (CC) configuration.