Both the input and output circuits share the emitter terminal. The output signal is taken between the collector and emitter, whereas the input signal is applied between the base and emitter.
- Significant power amplification is produced by the common emitter configuration's high voltage gain and high current gain.
- It is frequently utilized in numerous analog electrical circuits due to these qualities.
Circuit Diagram
In a common emitter amplifier circuit:
- The emitter terminal serves as the common reference point and is typically linked to ground.
- A coupling capacitor is used to apply the input signal to the base terminal.
- The collector terminal is where the output signal is obtained.
- To keep the transistor in the active area for appropriate amplification, biasing resistors are utilized.
Working Principle
The following describes how a common emitter amplifier works:
- The base terminal receives a little AC input signal.
- The input signal affects the base current.
- The collector current changes significantly as a result of transistor activity.
- The collector resistor allows the fluctuating collector current to pass through.
- The output signal is amplified as a result of the increased voltage variation at the collector.
- The output signal in this setup is 180° out of phase with the input signal.
Input Impedance
The ratio of input voltage to input current is known as the input impedance.
A common emitter amplifier may accept signals from a variety of electronic sources because of its reasonable input impedance.
Output Impedance
It is defined as the ratio of output voltage to output current when the input source is deactivated.
The output impedance of a CE amplifier is moderate to high, which aids in providing good voltage amplification.
Voltage Gain
The ratio of output voltage to input voltage is known as voltage gain.
Because the collector current varies greatly in relation to the base current, the common emitter amplifier offers a high voltage gain.
Advantages
- High Voltage Gain: Compared to alternative arrangements, this setup offers a considerable voltage amplification.
- High Current Gain: A considerably greater collector current is controlled by a tiny base current.
- Significant Power Gain: The total power gain is significant due to the high voltage and current gains.
- Frequently Used Configuration: Fit for a wide range of general-purpose amplification uses.
Disadvantages
- Phase Inversion: The input and output signals are 180 degrees out of phase.
- Moderate Input Impedance: Signal sources with extremely high impedance might not be a good fit.
- Limited High-Frequency Performance: At very high frequencies, the bandwidth may be reduced by the Miller effect.
Applications
- Audio Amplifiers: Used in audio systems to amplify sound signals.
- Signal Amplification Circuits: Used to increase the strength of weak electrical signals.
- Communication Systems: Used to amplify signals in transmitters and receivers.
- Multistage Amplifiers: Frequently employed as a stage in circuits for multistage amplifiers.
