Transistors are active devices (components with the ability to electrically control current flow) that can be used as a switch, an amplifier, or to match impedances.There are three different ways (configurations) to connect bipolar junction transistors.
The BJT has three terminal an emitter, a base, and a collector. Of the three possible ways of connecting the BJT the most used is the common emitter configuration.
COMMON EMITTER TRANSISTOR AMPLIFIER | |
PARAMETER | CHARACTERISTICS |
Voltage gain | Medium |
Current gain | Medium |
Power gain | High |
Input impedance | Medium |
Output impedance | Medium |
Input / output phase | 180° |
Q1 — NPN Bipolar Junction Transistor
R1 — R1 and R2 voltage divider provides DC bias
R2 – Develops the AC input signal
R3 – Collector load resistor, Develops the AC output
R4 – Emitter resistor prevents degeneration
C1 – DC blocking capacitor isolates bias from external DCC2 – bypass capacitor to hold the emitter to AC groundC3 –Coupling capacitor to couple the AC output signal |
