CE Amplifier with Emitter Resistor and Bypass Capacitance

CE AMPLIFIER WITH EMITTER RESISTOR AND BYPASS CAPACITANCE

A common emitter amplifier circuit is shown in Fig.2.17, the circuit consists of biasing resistors R₁ and R₂, the temeprature stabilization resistor R_E collector resistor R_C.

The bypass capacitor 'C' is used to eliminate ac degeneration ie it bypass all ac signal and increase the output gain.

i. The coupling capacitor C₁ connects the signal source with the transistor base. C₂ couples external load resistor R_L to the collector of transistor.

ii. C₁ and C₂ avoids the loading effect between input and output.

Operation

When the input voltage is increased in positive direction, V_BE is increased. Thus collector current I_C increases, the voltage drop occurs across R_C.

Apply KVL to collector circuit,

Input Impedance

Apply KVL to input circuit

We know that 

Output Impedence

Looking into emitter and collector terminal

The output impedance is given by

Voltage gain

Current Gain

Load Current

Power Gain

Characteristics of CE Amplifier

i. Good voltage gain

ii. Phase inversion i.e., output voltage is 180° out of phase with input

iii. Good current gain and power gain

iv. High input and output impedance

Applications

i. Voltage amplifier