Explain the concept of common-collector configuration in bipolar transistors.
1 Answer
The common-collector configuration, also known as the emitter-follower configuration, is one of the three basic configurations used in bipolar transistor circuits. The other two are common-emitter and common-base configurations. In the common-collector configuration, the emitter of the bipolar transistor is connected to a common point (usually ground), which is shared between the input and output sides of the circuit. The collector is connected to the positive power supply, and the base is the input terminal.
Here's a more detailed explanation of the common-collector configuration:
Transistor terminals:
Base (B): The input terminal through which the input current flows.
Emitter (E): The terminal connected to a common reference point, typically ground.
Collector (C): The output terminal that connects to the positive power supply.
Operating principle:
The common-collector configuration acts as a voltage buffer or impedance matching circuit. It has a high input impedance and a low output impedance, making it useful for coupling stages with different impedance levels. The input voltage (Vin) is applied to the base, and the output voltage (Vout) is taken across the emitter resistor (Re).
Amplification:
The common-collector configuration has a voltage gain slightly less than unity (less than 1). This means that the output voltage follows the input voltage closely, resulting in minimal voltage amplification. However, it provides current gain, as the output current (Ie) can be significantly larger than the input current (Ib). The ratio of output current to input current is known as the current gain (β), and it is typically higher than one.
Characteristics and applications:
High input impedance: The input impedance of the common-collector circuit is relatively high, which means it doesn't load down the previous stage of the circuit, making it suitable for impedance matching between different circuit blocks.
Low output impedance: The output impedance is relatively low, allowing the circuit to drive low-impedance loads effectively.
Voltage follower: The common-collector configuration is often used as a voltage follower, meaning the output voltage follows the input voltage with minimal attenuation.
Buffering: Due to its high input impedance and low output impedance, the common-collector configuration is commonly used as a buffer between stages in electronic circuits.
Biasing:
Proper biasing is necessary for the transistor to operate in the active region and avoid saturation or cutoff. In the common-collector configuration, a voltage divider or other biasing techniques can be employed to set the base-emitter voltage (Vbe) appropriately.
Overall, the common-collector configuration is an important circuit arrangement in bipolar transistor circuits, offering useful properties like impedance matching, voltage following, and buffering capabilities.
Here's a more detailed explanation of the common-collector configuration:
Transistor terminals:
Base (B): The input terminal through which the input current flows.
Emitter (E): The terminal connected to a common reference point, typically ground.
Collector (C): The output terminal that connects to the positive power supply.
Operating principle:
The common-collector configuration acts as a voltage buffer or impedance matching circuit. It has a high input impedance and a low output impedance, making it useful for coupling stages with different impedance levels. The input voltage (Vin) is applied to the base, and the output voltage (Vout) is taken across the emitter resistor (Re).
Amplification:
The common-collector configuration has a voltage gain slightly less than unity (less than 1). This means that the output voltage follows the input voltage closely, resulting in minimal voltage amplification. However, it provides current gain, as the output current (Ie) can be significantly larger than the input current (Ib). The ratio of output current to input current is known as the current gain (β), and it is typically higher than one.
Characteristics and applications:
High input impedance: The input impedance of the common-collector circuit is relatively high, which means it doesn't load down the previous stage of the circuit, making it suitable for impedance matching between different circuit blocks.
Low output impedance: The output impedance is relatively low, allowing the circuit to drive low-impedance loads effectively.
Voltage follower: The common-collector configuration is often used as a voltage follower, meaning the output voltage follows the input voltage with minimal attenuation.
Buffering: Due to its high input impedance and low output impedance, the common-collector configuration is commonly used as a buffer between stages in electronic circuits.
Biasing:
Proper biasing is necessary for the transistor to operate in the active region and avoid saturation or cutoff. In the common-collector configuration, a voltage divider or other biasing techniques can be employed to set the base-emitter voltage (Vbe) appropriately.
Overall, the common-collector configuration is an important circuit arrangement in bipolar transistor circuits, offering useful properties like impedance matching, voltage following, and buffering capabilities.