Physics · Semiconductor Electronics : Materials, Devices And Simple Circuits · NEET
| Number of diodes | One diode | Two or four diodes |
| Halves used | Only positive half | Both halves |
| Output frequency | Same as input (50 Hz to 50 Hz) | Double the input (50 Hz to 100 Hz) |
| Efficiency | About 40.6 percent | About 81.2 percent |
Yes. In a half wave rectifier the output frequency is EQUAL to the input frequency. If input is 50 Hz, output is 50 Hz. If input is 60 Hz, output is 60 Hz. This is because only one pulse of current appears in each full AC cycle, so the pattern repeats once per input cycle, keeping the period (and frequency) unchanged. This is the opposite of a full wave rectifier, where output frequency is double the input.
In one full AC cycle there are two halves: one positive and one negative. The single diode conducts only in the positive half and blocks the negative half. So you get exactly ONE output pulse per input cycle. Since the output pattern repeats at the same rate as the input, the time period stays the same, and frequency = 1/period stays the same. In a full wave rectifier BOTH halves are used, giving two pulses per cycle, which halves the period and doubles the frequency.
Only ONE diode. That single diode conducts during the positive half cycle (forward biased) and blocks during the negative half cycle (reverse biased). A full wave rectifier needs two diodes with a centre-tap transformer, or four diodes in a bridge circuit.
During the negative half cycle the diode is reverse biased, so it does NOT conduct. No current flows through the load, and the output voltage is zero for that entire half. This is why half the input power is wasted and the output looks like separated humps with gaps in between.
No. It is pulsating DC (also called unidirectional). The current always flows in one direction, but its value keeps rising and falling and drops to zero every negative half. To make it smoother and closer to steady DC, a filter capacitor is added across the load to remove the AC ripple.
In half wave rectification, if the input frequency is 60 Hz, then the output frequency would be:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
50 Hz. The half wave rectifier output frequency is always equal to the input frequency, so 50 Hz input gives 50 Hz output.
It uses only one half of the AC input, so half the power is wasted, the output has large ripple, and its rectification efficiency is low (about 40.6 percent, half that of a full wave rectifier).
The ripple frequency equals the input frequency (for example 50 Hz). This is the same as the output pulse frequency because there is one pulse per cycle.
No. In the negative half cycle the diode is reverse biased and does not conduct, so output is zero during that half.
A half wave rectifier uses one diode, rectifies only one half of each cycle, and output frequency equals input frequency. A full wave rectifier uses two or four diodes, rectifies both halves, and output frequency is double the input frequency.
