Explain the concept of common-collector configuration in transistor amplifiers.
1 Answer
The common-collector configuration, also known as the emitter-follower configuration, is one of the three basic configurations used in transistor amplifiers, the other two being common-emitter and common-base. In this configuration, a bipolar junction transistor (BJT) is employed as the amplifying element.
The common-collector configuration has the following characteristics:
Transistor Arrangement: The BJT is connected with its collector and emitter terminals as common terminals. The input signal is applied to the base, and the output is taken from the emitter. The collector is usually connected to a DC voltage source.
Voltage Gain: The primary function of an amplifier is to provide voltage gain, which is the ratio of output voltage to input voltage. In the common-collector configuration, the voltage gain is slightly less than unity (less than 1). It means the output voltage follows the input voltage with a slight reduction.
High Input Impedance: The input impedance of the common-collector configuration is relatively high. This is advantageous when the input source has a high output impedance, as it allows for better matching and minimizes signal loss due to impedance mismatch.
Low Output Impedance: The output impedance of the common-collector configuration is relatively low. This property enables the amplifier to deliver a substantial amount of current to the load (e.g., another stage of the amplifier or a load resistor) without significant voltage drop across the output.
Unity Voltage Gain (approximately): As mentioned earlier, the voltage gain in the common-collector configuration is slightly less than unity, typically around 0.98 to 0.99. However, it provides a current gain greater than unity (greater than 1), which can be useful in specific applications.
Phase Relationship: The output voltage in the common-collector configuration is in phase with the input voltage. This characteristic makes it useful when a phase relationship between input and output signals needs to be maintained.
Stability and High Bandwidth: The common-collector configuration offers good stability and a wide bandwidth, making it suitable for applications that require high-frequency amplification.
Applications of the common-collector configuration include impedance matching between high and low impedance circuits, buffering signals to prevent loading effects, and in applications where voltage gain slightly less than unity with high input impedance and low output impedance is desirable.
Overall, the common-collector configuration provides a useful building block in electronic circuits and finds its application in various electronic devices, such as audio amplifiers, signal buffers, and voltage regulators.
The common-collector configuration has the following characteristics:
Transistor Arrangement: The BJT is connected with its collector and emitter terminals as common terminals. The input signal is applied to the base, and the output is taken from the emitter. The collector is usually connected to a DC voltage source.
Voltage Gain: The primary function of an amplifier is to provide voltage gain, which is the ratio of output voltage to input voltage. In the common-collector configuration, the voltage gain is slightly less than unity (less than 1). It means the output voltage follows the input voltage with a slight reduction.
High Input Impedance: The input impedance of the common-collector configuration is relatively high. This is advantageous when the input source has a high output impedance, as it allows for better matching and minimizes signal loss due to impedance mismatch.
Low Output Impedance: The output impedance of the common-collector configuration is relatively low. This property enables the amplifier to deliver a substantial amount of current to the load (e.g., another stage of the amplifier or a load resistor) without significant voltage drop across the output.
Unity Voltage Gain (approximately): As mentioned earlier, the voltage gain in the common-collector configuration is slightly less than unity, typically around 0.98 to 0.99. However, it provides a current gain greater than unity (greater than 1), which can be useful in specific applications.
Phase Relationship: The output voltage in the common-collector configuration is in phase with the input voltage. This characteristic makes it useful when a phase relationship between input and output signals needs to be maintained.
Stability and High Bandwidth: The common-collector configuration offers good stability and a wide bandwidth, making it suitable for applications that require high-frequency amplification.
Applications of the common-collector configuration include impedance matching between high and low impedance circuits, buffering signals to prevent loading effects, and in applications where voltage gain slightly less than unity with high input impedance and low output impedance is desirable.
Overall, the common-collector configuration provides a useful building block in electronic circuits and finds its application in various electronic devices, such as audio amplifiers, signal buffers, and voltage regulators.