Semi-Conductor Diode as a Rectifier (Physics-Lesson-19.9): Ordinarily electricity is provided to us in the form of alternating voltage but most of electronic devices operate by direct current (D.C). Therefore, it becomes necessary that we convert the alternating voltage to D.C. the process of converting alternating voltage into D.C. is known as rectification and the device used for this purpose is known as rectifier. Fig. 19. 14 (a) shows a diode used as a rectifier.
Vi is the input alternating voltage by which we want to pass a direct current through the load resistance RL. During the positive half cycle of the input voltage, the anode of the diode is at a positive potential, therefore, the diode is forward biased and flows through the load resistance RL. The direction of flow of current has been shown by the signs of arrow in fig. 19. 14 (a). As the resistance of the diode in forward biased condition is very small as compared to RL, therefore almost the whole of input voltage appears across RL as shown in Fig. 19. 14 (c).
During the negative half cycle of the input voltage, the anode of the diode is at a negative voltage, so it s reverse based and it does not allow the current to pass through the load resistance RL. Therefore, the voltage across RL remains zero as shown in fig. 19.14©. Thus the current through RL passes only in one direction and the voltage developed across it is also uni-directional. In this way, diode acts as a rectifier.
