Question

If a BJT is to be used as a switch, it must operate in____________

(a) Cut-off mode or active mode

(b) Active Mode or saturation mode

(c) Cut-off mode or saturation mode

(d) Cut-off mode or saturation mode or active mode

I got this question in an interview for job.

Question is taken from BJTs Device Strucutres and Physical Operations topic in section Bipolar Junction Triodes (BJTs) of Electronic Devices & Circuits

Answer 1

The correct choice is (c) Cut-off mode or saturation mode

The explanation is: A BJT operates as an amplifiers in active mode and as a switch in cut-off or saturation mode.