Filter:-

• The output of a rectifier contains dc component as well as ac component. The presence of ac component is undesirable and therefore must be removed from the rectifier output. The circuit which removes the unwanted ac component is called filter. Depending upon the circuit elements used in the filters, the filters are classified into following categories.

1. Inductor filter or L filter
2. Capacitor filter or C filter
3. Inductor Capacitor filter or LC filter
4. $\pi$filter

Full wave centre tapped rectifier with capacitor filter:-

• Capacitor filter is inexpensive and suitable for light loads.The capacitor is connected in parallel with load to bypass the ac components. The value of the capacitor is large enough . The circuit diagram of Full wave rectifier with capacitor filter and its input and output waveforms is as follows.

Operation:-

• Immediately when power is turned ON, the capacitor C gets charged through forward baised diode D1 to Vmax during the first quarter of the rectifier output.
• In the next quarter cycle from$\frac{\pi}{2}$ to $\pi$, the capacitor starts discharing through RL.As the capacitor is a large value the discharging is slow.
• During the next positive cycle i.e from$\pi$to$2\pi$ the input voltage increaces and a point is reached when it becomes greater than the capacitor voltage at that point then Diode D2 becomes forward biased which causes the capcitor to charge to Vmax.
• This process is reapeated and the output of the capacitor filter is a smooothed output which contains less ripples.