Question

What is the purpose of an emitter capacitor?

Answer 1

First of all, we understand a bypass capacitor. A bypass capacitor connected in Common-Emitter configuration is known as emitter capacitor. Capacitor is defined as an electrical instrument which stores and releases electricity in a circuit.

Complete answer:
The bypass capacitor is a capacitor that shorts A.C. signals to the ground in such a way that any A.C. noise that represents a D.C. signal is removed, producing a much cleaner and pure D.C. signal. A bypass capacitor basically bypasses A.C. noise that may be on a D.C. signal. It filters out A.C. signals so that a clean and pure D.C. signal goes out without various A.C. ripples.

Now let us understand about the Emitter Capacitor also known as Bypass Emitter Capacitor.
When an emitter resistance is added to a Common Emitter (CE) amplifier then the voltage gain is reduced while the input impedance increases. Whenever the bypass capacitor is connected in parallel with an emitter resistance, the voltage gain of the CE amplifier increases. If the bypass capacitor is removed, an extreme degeneration is produced in the amplifier circuit and the voltage gained will be reduced.

Thus, the sole purpose or role of an emitter capacitor is to avoid voltage gain drop.

Note: It must be noted that a capacitor is employed to conduct an alternating current either as a component or a group of components. Normally the A.C. component is removed from an A.C./D.C. combination and then the D.C. signal is freed so that it could pass through the bypassed component.