Doping Elements & Semiconductors

Transistor Amplifier Circuit

As a PNP or NPN transistor has only three electrode, one must be common connection for a two pair of terminals for input and output signals. Three possibilities for amplifier circuit are:

1.  Common Base

2.  Common Emitter

3.  Common Collector

The circuit are for NPN  transistor, but they are the same for PNP transistor with all polarities reversed. 

 

 

Characteristic	Common Base	Common Emitter	Common Collector
Signal into	Emitter	Base	Base
Signal Out	Collector	Collector	Emitter
Advantages	Stability	High gain	High Gain
Phase Inversion	No	Yes	No
Similar Vacuum Tube	Grounded Grid	Grounded Cathode	Grounded Plate