Question

Explain the working of n-p-n transistor in common base configuration.

Hint:

In a common base configuration, the input signal is applied to the base, and the amplified output signal is taken from the collector.

Answer 1

Step 1: Basic Structure of an n-p-n Transistor.
An n-p-n transistor consists of three layers: an n-type emitter, a p-type base, and an n-type collector. The emitter emits electrons into the base, which are then collected by the collector.
Step 2: Working in Common Base Configuration.
1. The emitter is connected to a low-voltage source, and the base is connected to a small input current. 2. A large collector current flows from the collector to the emitter when a small current is injected into the base. 3. The transistor is in active mode when the base-emitter junction is forward biased, and the collector-base junction is reverse biased. 4. The current through the collector is controlled by the small current through the base, but the voltage at the base remains constant (hence the name common base).
Step 3: Conclusion.
In the common base configuration, the transistor provides current amplification, with a large collector current being controlled by a small base current. The voltage across the base is constant, and the transistor provides high input impedance.