- Common- emitter circuits
- Common- collector circuits
- Common- base circuits
1. COMMON EMITTER CIRCUITS: When the emitter of a transistor is connected to a point that is common to the input and output circuits, the configuration is referred to as a common-emitter circuit. The common reference point is usually at ground potential. It has the best combination of current gain and voltage gain. The common-emitter configuration is often called a grounded- emitter circuit.
2. COMMON COLLECTOR CIRCUIT: When the collector of a transistor is connected to a point that is common to both the input and output circuit, the configuration is called a common- collector or grounded- collector circuit.
3. COMMON BASE CIRCUIT: When the base of a transistor is connected to a point that common to both the input and output circuit, the configuration is known as a common- base or grounded- base circuit.