Table of Contents
Junction diode as a full wave rectifier:
A full wave rectifier consists of a transformer, two junction diodes D1 and D2 and a load resistance RL. The input a.c. signal is fed to the primary coil P of the transformer. The two ends A and B of the secondary S are connected to the p-ends of diodes D1 and D2 The secondary is tapped at its central point T which is connected to the π-ends of the two diodes through the load resistance RL’ as shown in fig.
Working:
At any instant, the voltages at the end A (input of D1) and end B (input of D2) of the secondary with respect to the centre tap T will be out of phase with each other. Suppose during the positive half cycle of a.c. input, the end A is positive and the end B is negative with respect to the centre tap T. Then the diode D1 gets forward biased and conducts current along the path AD1 XYTA, as indicated by the solid arrows. The diode D2 is reverse biased and does not conduct. During the negative half cycle, the end A becomes negative and the end B becomes positive with respect to the centre tap T. The diode D1 gets reverse biased and does not conduct. The diode D2 conducts current along the path BD2 XYTB, as indicated by broken arrows. As during both half cycles of input a.c. the current through load RL flows in the same direction (X à Y), so we get a pulsating d.c. voltage across RL, as shown in below Fig. Since output voltage across the load resistance RL is obtained for both half cycles of input a.c., this process is called full wave rectification and the arrangement used is called full-wave rectifier.
