Here’s a comprehensive explanation of the three basic amplifier configurations—Common Emitter (CE), Common Collector (CC) (also known as Emitter Follower), and Common Base (CB)—focusing on their structure, signal characteristics, advantages, disadvantages, and typical applications.
🔷 1. Common Emitter (CE) Amplifier
🔧 Configuration
Input: Applied between base and emitter.
Output: Taken from collector and emitter.
Common terminal: Emitter is common to both input and output.
🔍 Key Characteristics
Property
Description
Voltage Gain
High
Current Gain
Moderate to high
Power Gain
High
Phase Shift
180° (inverted output)
Input Impedance
Moderate
Output Impedance
Moderate
✅ Advantages
Good for voltage and power amplification.
Most widely used configuration.
❌ Disadvantages
Inverts the signal (180° phase shift).
Less suitable for impedance matching.
🧰 Applications
General-purpose signal amplification.
Audio amplifiers.
Intermediate stages in amplifiers.
🔷 2. Common Collector (CC) Amplifier — Emitter Follower
🔧 Configuration
Input: Applied between base and collector.
Output: Taken from emitter and collector.
Common terminal: Collector is common.
🔍 Key Characteristics
Property
Description
Voltage Gain
Approximately 1 (unity gain)
Current Gain
High
Power Gain
Moderate
Phase Shift
0° (no inversion)
Input Impedance
High
Output Impedance
Low
✅ Advantages
Excellent buffer stage.
Good for impedance matching (high input, low output impedance).
No signal inversion.
❌ Disadvantages
No voltage gain.
Not suitable as a stand-alone amplifier where voltage amplification is needed.
🧰 Applications
Buffer between stages.
Driving low-impedance loads.
Voltage followers.
🔷 3. Common Base (CB) Amplifier
🔧 Configuration
Input: Applied between emitter and base.
Output: Taken from collector and base.
Common terminal: Base is common.
🔍 Key Characteristics
Property
Description
Voltage Gain
High
Current Gain
Less than 1
Power Gain
Moderate
Phase Shift
0° (no inversion)
Input Impedance
Very low
Output Impedance
High
Frequency Response
Very wide (good for high-frequency use)
✅ Advantages
Excellent high-frequency response.
Stable operation.
❌ Disadvantages
Low input impedance—requires careful design of the driving stage.
Limited current gain.
🧰 Applications
RF (radio frequency) amplifiers.
High-frequency signal amplification.
Impedance matching (for low-impedance sources to high-impedance loads).
🧠 Summary Table
Configuration
Voltage Gain
Current Gain
Phase Shift
Input Z
Output Z
Application
Common Emitter (CE)
High
High
180°
Medium
Medium
General amplification
Common Collector (CC)
≈1 (unity)
High
0°
High
Low
Buffering, impedance matching
Common Base (CB)
High
<1
0°
Low
High
High-frequency use
Would you like visual diagrams of these configurations or an example circuit analysis for one of them?