A common emitter amplifier is one of the most commonly used transistor amplifier configurations. It is characterized by the following:
* High voltage gain: The common emitter amplifier provides a high voltage gain, which is the ratio of the output voltage to the input voltage. This is because the transistor acts as a voltage-controlled current source, and the output voltage is proportional to the collector current, which is in turn controlled by the base current.
* Low input impedance: The common emitter amplifier has a low input impedance, which means that it draws a relatively large amount of current from the signal source. This is because the base-emitter junction of the transistor acts as a forward-biased diode, and the base current is proportional to the input voltage.
* High output impedance: The common emitter amplifier has a high output impedance, which means that it can drive a relatively large load without significantly affecting the output voltage. This is because the collector current is controlled by the base current, and the output voltage is proportional to the collector current.
* Phase inversion: The common emitter amplifier inverts the phase of the input signal, meaning that the output signal is 180 degrees out of phase with the input signal. This is because the transistor acts as a current amplifier, and the collector current is 180 degrees out of phase with the base current.
Applications of a Common Emitter Amplifier
Common emitter amplifiers are used in a wide variety of applications, including:
* Audio amplifiers: Common emitter amplifiers are used to amplify the audio signals from microphones, guitars, and other audio sources.
* Video amplifiers: Common emitter amplifiers are used to amplify the video signals from cameras, DVD players, and other video sources.
* Radio frequency amplifiers: Common emitter amplifiers are used to amplify the radio frequency signals from antennas and other radio sources.
* Industrial control systems: Common emitter amplifiers are used to control the speed of motors, the temperature of ovens, and other industrial processes.
Advantages and Disadvantages of a Common Emitter Amplifier
The following are some of the advantages of a common emitter amplifier:
* High voltage gain
* Low input impedance
* High output impedance
* Phase inversion
The following are some of the disadvantages of a common emitter amplifier:
* Nonlinearity: The common emitter amplifier is a nonlinear device, which means that the output signal is not proportional to the input signal.
* Temperature sensitivity: The common emitter amplifier is sensitive to temperature changes, which can cause the output voltage to drift.
* Noise: The common emitter amplifier can generate noise, which can interfere with the output signal.
Despite these disadvantages, the common emitter amplifier is a versatile and widely used amplifier configuration.