need of rectifier and filter.
Need of rectifier: Every electronics circuit needs a D.C. power source for its operation. The rectifier circuit is used to convert A.C. supply to unidirectional pulses .
Need of filter: A filter circuit is a device which removes unwanted A.C. component from rectified output, and allows only the D.C. components to reach the load. So filter is used to provide ripple free output.