Before we answer the questions A transistor has how many pn junctions lets understand the definition of transistor. A Transistor is a three-terminal semiconductor device that regulates current or voltage flow and works as a switching interface for signals. It consists of two p-n junctions formed by placing either p-type or n-type semiconductors between a pair of opposite types.
So it has 2 p-n Junctions.
A transistor has how many pn junctions ? a) 1 b) 2 c) 3 d) 4
Answer is b) 2
What is PNP transistor?
When N-type semiconductor is kept between two p-type semiconductors, it is known as the PNP transistor.
What is NPN transistor?
When P-type semiconductor is kept between two N-type semiconductors, it is known as the NPN transistor