Question

1) The biasing of a transistor deals specifically with ac voltages and currents. (True or False?)

2) An emitter bypass capacitor provides a low-impedance path for dc signals between the emitter terminal and ground. (True or False?)

3) The open-loop voltage gain of an op amp is the ratio of its output voltage to its differential input voltage. (True or False?)

Answer 1

1)False ; The biasing of transistor is known from DC analysis of transistor. In DC analysis all the ac sources are deactivated by their internal resistances.

(2)False ; An emitter bypass capacitor provides high impedance for dc signal in between emitter terminal and ground. Because for dc signal frequency f=0 so capacitive reactance is infinity. Hence capacitor acts as open circuit. So net impedance in between emitter terminal and ground is equal to impedance of emitter generally denoted by RE. But for ac signal capacitor acts as short circuited,so for ac signal impedance between emitter and ground is zero.

(3)True ; The open loop voltage gain is the ratio of output voltage to its differential input voltage i.e Vo = A*Vid => A=Vo/Vid where A=open loop gain, Vid= differential input voltage, Vo= output voltage. For ideal op-amp differential output voltage is zero, hence for ideal op-amp open loop gain is infinity.