Analog Electronics – Page 31
Comparison of BJT Amplifier Configurations
There are three basic transistor amplifier configurations:
- Common Emitter (CE)
- Common Base (CB)
- Common Collector (CC)
Each configuration has different gain and impedance characteristics.
1️⃣ Common Emitter Amplifier
- High voltage gain
- High current gain
- Moderate input impedance
- Moderate output impedance
- Phase shift = 180°
Voltage gain: Av ≈ − (hfe RL) / hie
2️⃣ Common Base Amplifier
- High voltage gain
- Current gain ≈ 1
- Low input impedance
- High output impedance
- No phase shift
Current gain: α ≈ Ic / Ie
3️⃣ Common Collector Amplifier (Emitter Follower)
- Voltage gain ≈ 1
- High current gain
- Very high input impedance
- Low output impedance
- No phase shift
Voltage gain ≈ 1
Important Comparison Table
| Parameter | CE | CB | CC |
|---|---|---|---|
| Voltage Gain | High | High | ≈1 |
| Current Gain | High (β) | ≈1 (α) | High |
| Input Impedance | Medium | Low | High |
| Output Impedance | Medium | High | Low |
| Phase Shift | 180° | 0° | 0° |
GATE Important Points
- CE is most widely used amplifier
- CB used for high-frequency applications
- CC used as buffer amplifier
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