Chapter 29, Problem 11Q

To determine

Transistor use as switch.

Answer to Problem 11Q

Solution:

Transistor can be used as switch in cutoff (act as OFF)and saturation region (act as ON).

Explanation of Solution

A transistor can be operated in three modes- active region, saturation region, cut off region.

In active region transistor operate as amplifier.

In cut off region and saturation region transistor operate as switch both regions were used to operate a transistor as switch.

In cut off region both the junction of transistor being reversed biased V_B< 0.7V means zero input current I_B= 0 so zero output current I_C and maximum collector voltage V_CE which results in large depletion region and no current flows through the circuit and it act as switch off state.

In saturation region both the junctions are forward bias V_B > 0.7V, maximum applied current so maximum collector current Ic and minimum collector voltage V_CE which results in small depletion region and maximum current flows through circuit. In this region transistor act as switch ON state.