Question

How is the p-n junction diode used as the full wave rectifier ? Explain its working by drawing simple circuit.

Hint:

The key to the full-wave rectifier is the center-tapped transformer, which effectively splits the AC input into two out-of-phase sources, allowing one diode to conduct during the positive half and the other to conduct during the negative half, with both driving the current in the same direction through the load.

Answer 1

Step 1: Understanding the Concept: 
A full-wave rectifier is an electronic circuit that converts both halves (positive and negative) of an alternating current (AC) input into a pulsating direct current (DC) output. It uses two p-n junction diodes and a center-tapped transformer. The basic principle is that a p-n junction diode allows current to flow only when it is forward-biased. 
Step 2: Circuit Diagram and Waveforms: 

During the positive half-cycle of the AC input: The end A of the secondary coil is positive with respect to the center tap C, and the end B is negative. This makes the diode \(D_1\) forward-biased and the diode \(D_2\) reverse-biased. As a result, current flows through diode \(D_1\) and the load resistor \(R_L\) from top to bottom. No current flows through \(D_2\). 
During the negative half-cycle of the AC input: The polarity reverses. The end A becomes negative, and the end B becomes positive with respect to the center tap C. This makes diode \(D_2\) forward-biased and diode \(D_1\) reverse-biased. Current now flows through diode \(D_2\) and the load resistor \(R_L\). Importantly, the direction of current through \(R_L\) is again from top to bottom. \end{enumerate} In both half-cycles, the current flows through the load resistor in the same direction. Therefore, we get a continuous, pulsating DC voltage across the load, as shown in the output waveform diagram. 
Step 4: Final Answer: 
A full-wave rectifier uses a center-tapped transformer and two diodes to convert both halves of the AC cycle into a unidirectional (DC) output, making it more efficient than a half-wave rectifier.