Half Wave Rectifier: The circuit diagram for junction diode as half wave rectifier is shown in below Fig.
Let during first half the cycle the secondary terminal S1 of transformer be positive relative to S2, then the junction diode is forward biased. Therefore the current flows and its direction in load resistance RL is from A to B. In next half cycle the terminal S1 is negative relative to S2 then the diode is in reverse bias, therefore no current flows in diode and hence there is no potential difference across load RL. Therefore the output current in load flows only when S1 is positive relative to S2. That is during first half cycles of input a.c. signal there is a current in circuit and hence a potential difference across load resistance RL while no current flows for next half cycle. The direction of current in load is always from A to B. Thus a single p-n junction diode acts as a half wave rectifier. The input and output waveforms of half wave rectifier are shown in the below figure.
