1) What is the major difference between a bipolar and a unipolar device?

2. Which of the transistor currents is always the largest? Which is always the smallest? Which two currents are relatively close in magnitude?

Answers:

1. What is the major difference between a bipolar and a unipolar device?

Ans. Bipolar devices (bipolar transistors) can have both minority and majority carriers (electrons and holes) flowing, whereas Unipolar devices (FETs) only have majority carriers (either electrons or holes) flowing. The fact that bipolar transistors have two types of carriers flowing simultaneously results in the name 'bi-polar'. The monirity carrier flow is responsible for collector conduction modulation and transistor storage time.

2. Which of the transistor currents is always the largest? Which is always the smallest? Which two currents are relatively close in magnitude?

Ans. In a transistor being a three terminal device namely Emitter, Collector and Base, it has three currents flowing through it. Base current, Emitter current and Collector current.

EMITTER current is the largest among three which is equal to sum of the COLLECTOR and BASE currents.

IE = IB + IC where IE ---> Emitter Current, IB----> Base Current and IC---> Collector Current

BASE current is very small in magnitude and in the order of few microamps, where as Collector current is very much greater than base current which is in the order of milli amps. Therefore, COLLECTOR current and EMITTER currents are relatively CLOSE in magnitude.

IE ~~ IC