The common-emitter (CE) and common-collector (CC) configurations are two fundamental transistor amplifier configurations used in electronic circuits, particularly with bipolar junction transistors (BJTs). Here are the main differences between them:
### Common-Emitter Configuration
1. **Configuration**: In a common-emitter configuration, the emitter terminal of the transistor is common to both the input and output circuits.
2. **Input and Output**:
- **Input**: Applied between the base and emitter.
- **Output**: Taken between the collector and emitter.
3. **Voltage Gain**: Provides a high voltage gain. The output voltage can be significantly greater than the input voltage.
4. **Phase Shift**: Inverts the input signal, meaning a positive change in the input results in a negative change in the output.
5. **Input Impedance**: Generally low input impedance, making it more sensitive to changes in input signal.
6. **Output Impedance**: Relatively high output impedance.
7. **Applications**: Used in amplification circuits, switches, and oscillators.
### Common-Collector Configuration
1. **Configuration**: In a common-collector configuration, the collector terminal of the transistor is common to both the input and output circuits.
2. **Input and Output**:
- **Input**: Applied between the base and collector.
- **Output**: Taken between the emitter and collector.
3. **Voltage Gain**: Provides a voltage gain of approximately 1 (unity gain), meaning the output voltage is nearly equal to the input voltage.
4. **Phase Shift**: Non-inverting configuration; the output phase remains the same as the input phase.
5. **Input Impedance**: High input impedance, making it less sensitive to input changes.
6. **Output Impedance**: Low output impedance, making it suitable for driving loads.
7. **Applications**: Often used as a buffer (emitter follower) to match impedance between circuits, voltage level shifting, and signal isolation.
### Summary
- **Common-Emitter**: High voltage gain, inverts signal, low input impedance, high output impedance.
- **Common-Collector**: Unity gain, non-inverting, high input impedance, low output impedance.
Both configurations serve different purposes in circuit design, and the choice between them depends on the specific requirements of the application.