To use BJT Transistor as an amplifier we need to make sure that the Q point is properly adjusted to do the amplification. To set the Q point we need to do the proper biasing to the transistor. When we talk about biasing a BJT Transistor, we normally mean to apply the external power supply in the right polarity so that the junctions could work in the right order and we can use them for our purpose. By adjusting a propper Q point we can use BJT Transistor as a switch or we may use the BJT Transistor as an Amplifier. And in today’s post, we are going to talk about the BJT Transistor as an Amplifier. While doing the biasing we need to be careful that the Base-Emitter junction is always forward bias, and the collector-base junction is always reverse biased.
BJT Transistor Configurations
There are different ways of biasing, mostly it depends on which configuration you are using the BJT Transistor. As you may already know that there are three main configurations of the BJT Transistor. Because BJT has three terminals and for input, we need two terminals and for output, we need two terminals as well. But for the BJT Transistor, we only have three terminals. So to justify, we need to share one terminal in output and input. The name of that configuration is according to the common terminal. So if we are sharing the Emitter terminal between input and Output, we call it Common Emitter Configuration and if we are sharing the Base Terminal between input and output, we call it Common Base Configuration and finally, if we share Collector, we call it Common Collector Configuration. Sometimes these configurations are also referred to as CE, CB and CC respectively.
BJT Transistor Amplifier types
Just like the different configurations of the BJT Transistor, which we just discussed, there are also different types of BJT Transistor Amplifiers. These are
- Class A Amplifier
- Class B Amplifier
- Class C Amplifier
There are different applications of each. As well as the different pros and cons of every class.