The choice between common emitter (CE), common base (CB), and common collector (CC) transistor configurations depends largely on the specific application requirements and the desired circuit characteristics.
Among the three configurations, the common emitter (CE) configuration is arguably the most popular and versatile in practical applications. In a CE configuration, the input signal is applied to the base with respect to the emitter, and the output is taken from the collector with respect to the emitter. This configuration offers significant voltage gain, current gain, and power gain, making it suitable for use in amplification stages of audio amplifiers, voltage amplifiers, and signal processing circuits. The CE configuration provides high input impedance and moderate output impedance, making it easier to interface with other circuits.
The common base (CB) configuration, on the other hand, is less common in general-purpose amplifier circuits but finds use in applications requiring high-frequency operation. In a CB configuration, the input signal is applied to the emitter with respect to the base, and the output is taken from the collector with respect to the base. CB transistors offer low input impedance and high voltage gain, making them suitable for high-frequency amplification stages in radio frequency (RF) amplifiers and oscillators where impedance matching and high-frequency response are critical.
The common collector (CC) configuration, also known as the emitter follower, is primarily used for impedance matching and buffering purposes. In a CC configuration, the input signal is applied to the base with respect to the emitter, and the output is taken from the emitter with respect to the collector. CC transistors provide unity voltage gain (approximately), low output impedance, and high input impedance. This configuration is useful in applications where voltage buffering, signal isolation, or impedance transformation is required, such as in voltage regulators and signal impedance matching circuits.
In summary, while each transistor configuration (CE, CB, CC) has its advantages and is suitable for specific applications, the common emitter (CE) configuration remains the most widely used due to its versatility, high gain characteristics, and ease of implementation in various amplifier and signal processing circuits. The choice of configuration depends on factors such as desired gain, impedance characteristics, frequency response, and the specific requirements of the circuit being designed.