Question

Draw a circuit diagram of a full-wave rectifier using p-n junction diodes. Explain its working and show the input-output waveforms.

Hint:

Full-wave rectifier facts:

Uses both half cycles
Output frequency doubles
Can be centre-tapped or bridge type

Answer 1

Full-Wave Rectifier Using P-N Junction Diodes
A full-wave rectifier converts the entire alternating current (AC) input into pulsating direct current (DC), allowing both halves of the AC waveform to contribute to the output. It typically uses four p-n junction diodes arranged in a bridge configuration. 
- D1, D2, D3, D4: P-N junction diodes - AC: Alternating current source - RL: Load resistor across which DC is obtained 

Working:
1. Positive Half-Cycle of AC Input:
- During the positive half of the AC input, the current flows through diode D1 → Load resistor RL → D3. - Diodes D2 and D4 remain reverse-biased and do not conduct. - A positive voltage appears across RL.
2. Negative Half-Cycle of AC Input:
- During the negative half of the AC input, the current flows through D2 → Load resistor RL → D4. - Diodes D1 and D3 remain reverse-biased. - The current through RL remains in the same direction, so the output is still positive.
Thus, both halves of the AC input contribute to the output voltage, doubling the frequency of the pulsating DC compared to a half-wave rectifier. 
Input-Output Waveforms:
- Input AC waveform:
- Output DC waveform (pulsating):
Summary:
- A full-wave rectifier uses four p-n junction diodes in a bridge configuration. - Both halves of the AC waveform are used, producing a pulsating DC output. - The output frequency is twice the input AC frequency. - Smoother DC can be obtained by adding a filter capacitor across the load resistor RL.