Question

The Transistor configuration most suitable for impedance matching is ______.
1. Common base
2. Common Emitter
3. Common Collector
4. None of these

Answer 1

Correct Answer - Option 3 : Common Collector

• Common collector configuration, also known as emitter follower provides high input impedance and low output impedance. So they are used for the purpose of impedance matching.
• In common collector configuration, the collector terminal is common to both input and output terminals. The current gain in the common-collector configuration is therefore the ratio of the emitter current to the base current.
• Since the emitter current is very high as compared to the base current, we get current amplification.
• It provides a voltage gain of less than unity.

 

Important Differences between different transistor configuration is as shown:

Parameter	Common-Base	Common-Emitter	Common-Collector
Input Current	IE	IB	IB
Output Current	IC	IC	IE
Current Gain	\({\alpha _{dc}} = \frac{{{I_C}}}{{{I_E}}}\)	\({\beta _{dc}} = \frac{{{I_C}}}{{{I_B}}}\)	\(\gamma = \frac{{{I_E}}}{{{I_B}}} \) \({1 + {\beta _{dc}}}\)
Voltage Gain	Medium	Medium	Less Than 1