Transistor Configuration refers to the three basic transistor configurations indicates the transistor terminal that is common to both input and output circuits. This gives rise to the three terms: Common Base (CB), Common Collector (CC), and Common Emitter (CE).
The term common is used to denote the element that is common to both input and output circuits. Since in transistor, the common element is often grounded, these configurations are frequently referred to as grounded emitter, grounded base, and grounded collector.
In designing a transistor circuit it is necessary to adopt the transistor circuit configuration that will provide the required attributes.