Physics · Semiconductor Electronics : Materials, Devices And Simple Circuits · NEET
| Number of diodes | 1 diode | 2 diodes (centre-tap) or 4 (bridge) |
| Part of cycle used | Only one half of each cycle | Both halves of each cycle |
| Output frequency (50 Hz input) | Same, 50 Hz | Double, 100 Hz |
| Ripple factor | High, about 1.21 | Low, about 0.48 |
| Max efficiency | About 40.6% | About 81.2% |
| Output quality | Wavy, has gaps | Smoother, no gaps |
A half wave rectifier uses just 1 diode. A full wave rectifier uses 2 diodes with a centre-tapped transformer, or 4 diodes in a bridge circuit (no centre tap needed). NEET usually shows the 2-diode centre-tapped version. Remember: each diode in the full wave circuit conducts for one half cycle, so together they cover the full cycle.
In a half wave rectifier, only one half-cycle passes per input period. So one output pulse appears in the same time as one input cycle, and output frequency = input frequency. In a full wave rectifier, both halves of every input cycle become an output pulse, so you get two pulses per input cycle and output frequency = 2 times input frequency. For 50 Hz mains: half wave output = 50 Hz, full wave output = 100 Hz.
The half wave rectifier is worse on both. Its ripple factor is about 1.21 (high, means a very wavy output) and its maximum efficiency is only about 40.6%. The full wave rectifier has a lower ripple factor of about 0.48 and a higher maximum efficiency of about 81.2%. Lower ripple and higher efficiency are why full wave is preferred in real power supplies.
No. Even though it uses the negative half of the input, the full wave circuit flips that negative half so the output is always in one direction (all positive pulses). The output is still unidirectional (DC-like pulses), just with no gaps between pulses. This is why it looks smoother than half wave output, which has empty gaps where the negative half was blocked.
Yes. Both rectifier outputs are pulsating (not steady DC). A filter capacitor is added across the load to smooth these pulses toward steady DC by charging at peaks and discharging through the load. Because full wave pulses are closer together (double frequency, no gaps), the same capacitor smooths them better, giving cleaner DC than in half wave.
In half wave rectification, if the input frequency is 60 Hz, then the output frequency would be:
A full wave rectifier circuit with diodes D1 and D2 is shown in the figure. If the input supply voltage is V_in = 220 sin(100 pi t) volt, then at t = 15 ms, which diode conducts?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
A half wave rectifier converts only one half of each AC cycle to DC using 1 diode, wasting the other half. A full wave rectifier converts both halves using 2 (centre-tapped) or 4 (bridge) diodes, giving a smoother, more efficient DC output.
Half wave output = 50 Hz (same as input). Full wave output = 100 Hz (double the input), because it produces two pulses per input cycle.
The full wave rectifier is more efficient. Its maximum efficiency is about 81.2%, compared to about 40.6% for the half wave rectifier, because it uses both halves of the input.
Half wave ripple factor is about 1.21 (high, wavy output). Full wave ripple factor is about 0.48 (smoother output). Lower ripple means cleaner DC.
Two diodes with a centre-tapped transformer, or four diodes in a bridge rectifier that does not need a centre tap. A half wave rectifier needs only one diode.
