What are common-emitter, common-base, and common-collector transistor configurations?
1 Answer
The common-emitter, common-base, and common-collector are three basic configurations used in transistor circuits, representing different ways to connect the transistor's terminals. These configurations determine how the input and output signals are related and how the transistor amplifies or attenuates the signals. Let's take a closer look at each configuration:
Common-Emitter (CE) Configuration:
In the common-emitter configuration, the emitter terminal is shared between the input and output circuits, while the base is the input and the collector is the output. It is the most commonly used configuration for bipolar junction transistors (BJTs) and offers high voltage and current gain.
Characteristics of the Common-Emitter Configuration:
Voltage gain is relatively high.
Current gain (beta or hFE) is significant.
The input is applied to the base-emitter junction, and the output is taken from the collector-emitter junction.
The input is in phase with the output.
Applications: Common-emitter amplifiers are used in audio amplifiers, voltage amplifiers, and most general-purpose transistor applications.
Common-Base (CB) Configuration:
In the common-base configuration, the base terminal is shared between the input and output circuits, while the emitter is the input and the collector is the output. This configuration provides a low input impedance and voltage gain of less than one, but it offers high current gain.
Characteristics of the Common-Base Configuration:
Voltage gain is typically less than one.
High current gain (alpha or hFE) is obtained.
The input is applied to the emitter-base junction, and the output is taken from the collector-base junction.
The input and output signals are in phase.
Applications: Common-base configurations are used in RF (radio frequency) amplifiers, high-frequency applications, and impedance matching circuits.
Common-Collector (CC) Configuration:
In the common-collector configuration, the collector terminal is shared between the input and output circuits, while the base is the input and the emitter is the output. This configuration is also known as the emitter-follower configuration. It provides unity voltage gain (voltage follower) but offers high current gain.
Characteristics of the Common-Collector Configuration:
Voltage gain is approximately one (unity gain).
High current gain (beta or hFE) is achieved.
The input is applied to the base-emitter junction, and the output is taken from the collector-emitter junction.
The input and output signals are in phase.
Applications: Common-collector configurations are often used as voltage buffers to provide impedance matching between high and low impedance circuits, to reduce loading effects, or as impedance converters.
Each transistor configuration has its specific applications based on the desired signal amplification or attenuation characteristics and the impedance matching requirements of the overall circuit design.
Common-Emitter (CE) Configuration:
In the common-emitter configuration, the emitter terminal is shared between the input and output circuits, while the base is the input and the collector is the output. It is the most commonly used configuration for bipolar junction transistors (BJTs) and offers high voltage and current gain.
Characteristics of the Common-Emitter Configuration:
Voltage gain is relatively high.
Current gain (beta or hFE) is significant.
The input is applied to the base-emitter junction, and the output is taken from the collector-emitter junction.
The input is in phase with the output.
Applications: Common-emitter amplifiers are used in audio amplifiers, voltage amplifiers, and most general-purpose transistor applications.
Common-Base (CB) Configuration:
In the common-base configuration, the base terminal is shared between the input and output circuits, while the emitter is the input and the collector is the output. This configuration provides a low input impedance and voltage gain of less than one, but it offers high current gain.
Characteristics of the Common-Base Configuration:
Voltage gain is typically less than one.
High current gain (alpha or hFE) is obtained.
The input is applied to the emitter-base junction, and the output is taken from the collector-base junction.
The input and output signals are in phase.
Applications: Common-base configurations are used in RF (radio frequency) amplifiers, high-frequency applications, and impedance matching circuits.
Common-Collector (CC) Configuration:
In the common-collector configuration, the collector terminal is shared between the input and output circuits, while the base is the input and the emitter is the output. This configuration is also known as the emitter-follower configuration. It provides unity voltage gain (voltage follower) but offers high current gain.
Characteristics of the Common-Collector Configuration:
Voltage gain is approximately one (unity gain).
High current gain (beta or hFE) is achieved.
The input is applied to the base-emitter junction, and the output is taken from the collector-emitter junction.
The input and output signals are in phase.
Applications: Common-collector configurations are often used as voltage buffers to provide impedance matching between high and low impedance circuits, to reduce loading effects, or as impedance converters.
Each transistor configuration has its specific applications based on the desired signal amplification or attenuation characteristics and the impedance matching requirements of the overall circuit design.