What are the different types of transistor amplifiers (common-base, common-gate, etc.)?
1 Answer
Transistor amplifiers are electronic circuits that use transistors to increase the amplitude of a signal. There are three primary transistor amplifier configurations based on how the transistor's terminals (base, emitter, and collector) are connected to the input and output signals: common-base, common-emitter, and common-collector (also known as emitter follower). In addition to these, there is a similar configuration for field-effect transistors (FETs) called common-gate.
Common-Base Amplifier:
In the common-base configuration, the input signal is applied to the emitter terminal, the output is taken from the collector terminal, and the base terminal is the common terminal. The input and output signals are in phase with each other. This configuration provides high voltage gain and low current gain but has low input impedance and high output impedance. It is often used in high-frequency applications.
Common-Emitter Amplifier:
The common-emitter configuration is the most commonly used transistor amplifier. The input signal is applied to the base terminal, the output is taken from the collector terminal, and the emitter terminal is the common terminal. This configuration offers both voltage and current amplification, providing high voltage gain and moderate current gain. It has moderate input and output impedance, making it suitable for various applications, including audio amplification.
Common-Collector (Emitter Follower) Amplifier:
In the common-collector configuration (also known as the emitter follower), the input signal is applied to the base terminal, the output is taken from the emitter terminal, and the collector terminal is the common terminal. This configuration provides unity voltage gain (voltage follower) but has high current gain. It has very high input impedance and low output impedance, making it ideal for impedance matching and buffering applications.
Common-Gate Amplifier (FET):
The common-gate configuration is the FET counterpart to the common-base bipolar transistor configuration. In the common-gate amplifier, the input signal is applied to the gate terminal, the output is taken from the drain terminal, and the source terminal is the common terminal. This configuration provides a similar function to the common-base amplifier, offering high voltage gain and low current gain.
These amplifier configurations are fundamental building blocks in analog electronics, and each has its specific advantages and applications based on the requirements of a particular circuit. Designers select the appropriate configuration depending on the desired characteristics, such as gain, impedance matching, and frequency response.
Common-Base Amplifier:
In the common-base configuration, the input signal is applied to the emitter terminal, the output is taken from the collector terminal, and the base terminal is the common terminal. The input and output signals are in phase with each other. This configuration provides high voltage gain and low current gain but has low input impedance and high output impedance. It is often used in high-frequency applications.
Common-Emitter Amplifier:
The common-emitter configuration is the most commonly used transistor amplifier. The input signal is applied to the base terminal, the output is taken from the collector terminal, and the emitter terminal is the common terminal. This configuration offers both voltage and current amplification, providing high voltage gain and moderate current gain. It has moderate input and output impedance, making it suitable for various applications, including audio amplification.
Common-Collector (Emitter Follower) Amplifier:
In the common-collector configuration (also known as the emitter follower), the input signal is applied to the base terminal, the output is taken from the emitter terminal, and the collector terminal is the common terminal. This configuration provides unity voltage gain (voltage follower) but has high current gain. It has very high input impedance and low output impedance, making it ideal for impedance matching and buffering applications.
Common-Gate Amplifier (FET):
The common-gate configuration is the FET counterpart to the common-base bipolar transistor configuration. In the common-gate amplifier, the input signal is applied to the gate terminal, the output is taken from the drain terminal, and the source terminal is the common terminal. This configuration provides a similar function to the common-base amplifier, offering high voltage gain and low current gain.
These amplifier configurations are fundamental building blocks in analog electronics, and each has its specific advantages and applications based on the requirements of a particular circuit. Designers select the appropriate configuration depending on the desired characteristics, such as gain, impedance matching, and frequency response.