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A transistor has three terminals: emitter, base, and collector. Using these three terminals, the transistor may be linked in a circuit in three distinct ways, with one terminal common to both input characteristics and output characteristics. Common Base, Common Emitter, and Common Collector configurations are the three sorts of setups. The emitter junction is forward biased, and the collector junction is reverse biased in all configurations. Each has unique gain, input and output impedance, input characteristics, etc. Consequently, a specific configuration will be chosen throughout the electrical circuit design process. Let us understand these configurations in detail.
Common emitter transistor configuration
The name suggests that the Emitter terminal is used as a common terminal for both the transistor’s input and output characteristics. The NPN transistor and PNP transistors have the same emitter connection. This transistor arrangement is most likely the most common. The circuit has an output impedance and medium input impedance. Both current and voltage gain is in the middle, but the output is the inverse of the input, resulting in a 180° phase reversal. As a result of its high overall performance, this is often the most regularly utilized arrangement.
Automated gain can manage the variations, but the transistor in a common-emitter architecture may go into shutdown or oscillation, and the output might clip. Two significant problems affect common-emitter circuits, which may be avoided with proper circuit design. One concern is that the gain of an amplifier in a common-emitter architecture might be high and unpredictable due to manufacturing variances, temperature, and bias current.
Common collector (emitter follower) configuration
The name suggests that the Collector terminal is a common terminal for both the transistor’s input characteristics and output characteristics. The NPN and PNP transistors share a similar collector connection. As in CB and CE topologies, the emitter junction is forward biased, whereas the collector junction is reverse biased. The flow of electrons is managed in the same way. The input current is the base current, and the output current is the emitter current.
As a result, since its input impedance is more significant than its output impedance, this gadget is often used as an impedance-matching circuit. It is often utilized in digital circuits in combination with logic gates. The common-collector transistor is classified as an emitter follower because the voltage gain of the emitter follower is about 0.6 V lower than the voltage gain of the base. Instead of typical voltage gain, it is utilized for impedance matching and current gain. Input impedance substantially surpasses output impedance, as in the common-emitter circuit.
Common base transistor configuration
The name suggests that the Collector terminal is a common terminal for both the transistor’s input characteristics and output characteristics. The NPN and PNP transistors share a similar collector connection. As in CB and CE topologies, the emitter junction is forward biased, whereas the collector junction is reverse biased. The flow of electrons is managed in the same way. The input current is the base current, and the output current is the emitter current. This circuit provides a voltage gain that is less than one. The emitter current is equal to the sum of collector and base currents. The input characteristics and output characteristics signals are synchronized. This design serves as the output of a non-inverting amplifier. This circuit is usually used to match impedance. That is, to power a low-impedance load with a high-impedance supply.
The standard base design has no phase inversion between the emitter and collector. As a result, the waves at the input and output characteristics are in sync, and the amp is non-inverting. A reason for the common-base amplifier’s limited application is its impedance with low input. It is also called a current follower, since the common-base output might be high. A common-base amplifier’s current gain (alpha) usually tends to be unity. The voltage increases, on the other hand, maybe anything in the bracket of 100 and 2,000. The bias resistors determine everything.
Conclusion
A transistor is a semiconductor device that can conduct and insulate electric current or voltage. A transistor serves as both a switch and an amplifier. Transistors are essential components in the majority of electrical gadgets used today. The transistor, invented in 1947 by three American scientists, John Bardeen, Walter Brattain, and William Shockley, is regarded as one of the most significant innovations in science.
