Question

Answer the following:

A. What does BJT means? and why is it called BJT?

B. What are the two types of BJT? Explain their difference and commonalities, as well as their basic operation.

C. What are the three basic configurations of BJT transistor? Explain its input and output characteristics.

Answer 1

BJT means Bipolar Junction Transistor. BJT is a type of transistor that uses both electron and hole charge carriers .

There are two types of BJT transistors. they are NPN and PNP BJT trasnsitors.

Difference between NPN and PNP transistors

PNP	NPN
1.small amount of current also flows from emitter to base	1.small amount of current flows from base to emitter.
2.In PNP base is lower voltage	2.In NPN base is a higher voltage.
3.The emitter is heavily p-doped compared to collector.so emitter and collector are not interchangeable.	3.The emitter is heavily N-doped compared to collector.so emitter and collector are not interchageable.

Basic operation of PNP Bjt transistor

Basically , in this type of transistor construction the two diodes are reversed with respec to giving positive negative positive type of configuration,with the arrow which also defines the emitter terminal this time pointing inwards in the transistor symbol.

The PNPN transistor use a small base current and a negative base voltage to control a much larger emitter -collector current .

Basic operation of NPN transistor

If the base voltage is equal to the emitter voltage then the transistor is in OFF state. If the base voltage increase over emitter voltage then the transistor becomes more switched until it is in fully on state. If the sufficient postive voltage is applied to the base terminal. base terminal act as input to the collector emitter region acts as a output.

To allow the current flow between emiiter and collector properly.if the voltage is greater than a voltage drop .7 v otherwise the transistor will not operate.