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 DC
C2 – bypass capacitor to hold the emitter to AC ground
C3 –Coupling capacitor to couple the AC output signal
