Question

Which capacitor is used to block DC portion by allowing to pass only AC portion of the amplified signal to load?

(a) Input Coupling Capacitor

(b) Bypass Capacitor

(c) Output Coupling Capacitor

(d) Both coupling and bypass capacitor

I had been asked this question in quiz.

The doubt is from Comparison of Transistor Amplifier topic in portion Small-Signal Low-Frequency AC models of Transistors of Electronic Devices & Circuits

Answer 1

Right option is (c) Output Coupling Capacitor

The explanation: In RC coupled CE amplifier, the transistor is connected in common-emitter (CE) configuration and capacitors C1 & C2 are coupling capacitors.

Input coupling capacitor is used for coupling the ac input voltage to the transistor base. Inversely, the output coupling capacitor (C2) is used for coupling an output of an amplifier to the load resistance or to the next stage of an amplifier.

Besides these, input coupling capacitor blocks any DC element present in AC input voltage & couples only AC component of input signal whereas bypass capacitor offers a low reactance to the amplified AC signal.