Question

The negative sign in the formula of amplification factor indicates_________

(a) that IE flows into transistor while IC flows out it

(b) that IC flows into transistor while IE flows out it

(c) that IB flows into transistor while IC flows out it

(d) that IC flows into transistor while IB flows out it

This question was addressed to me during an interview for a job.

Query is from The Common Base Configuration topic in portion Transistor Characteristics of Electronic Devices & Circuits

Answer 1

The correct choice is (a) that IE flows into transistor while IC flows out it

The best I can explain: When no signal is applied, the ratio of collector current to emitter current is called dc alpha, αdc of a transistor. αdc=-IC/IE. It is the measure of the quality of a transistor. Higher is the value of α, better is the transistor in the sense that collector current approaches the emitter current.