Circuit Diagram:
Working : It consists of a filter capacitor C1 connected across the rectifier output, a choke L is series and another filter capacitor C2 connected across the load RL. The pulsating o/p from the rectifier is applied across the input terminals 1 & 2 of the filter. The filtering action of the three components C1,C2 and L is described below: The filter capacitor C1 offers low reactance to a.c component of rectifier output while it offers infinite reactance to the d.c. component. Therefore, capacitor C1 bypasses an appreciable amount of a.c component to the ground, while the d.c component moves towards L. The choke L offers high reactance to the a.c component but it offers almost zero reactance to the d.c component. Therefore, it allows the d.c component to flow through it, and blocks a.c component. The filter capacitor C2 bypasses the a.c component which the choke has failed to block. Therefore, only d.c component appears across the load.