BJT Common Emitter Configuration

Electronics

Bipolar Junction Transistors can be connected in three major configurations. The following schematic is for the most used of these configurations.

Common Emitter

R1 Set bias

R2 Set bias & develop input

R3 Develop the output

R4 Prevent Degeneration

C1 Coupling Capacitors to separate the AC signals from the DC biasing voltage. 

C2 Coupling Capacitors to    separate the AC signals from the DC biasing voltage.

C3 Bypass Capacitor 

Q1 2N2904 NPN BJT

Common Emitter Characteristics

The main characteristics of importance are input impedance, gain, and output impedance. Other important characteristics are input and output phase relationship and frequency response.

input impedance       Medium

Output impedance    Medium

Voltage gain               Medium

Current gain               Medium

Power gain                 High

Input/Output phase 180°

Common Emitter Application

Applications include amplifier, phase inverter, switch and much much more.

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