Browse over 10,000 Electronics Projects using the Page Numbering provided at the bottom of each Page.

SDTV Reconstruction Filter with Adjustable Group Delay

SDTV Reconstruction Filter with Adjustable Group Delay

The MAX4450 operational amplifier configured in a 3-pole, low-pass Sallen-Key filter provides a Butterworth response with a bandwidth of 3dB at 5.25MHz. This circuit can be used for video anti aliasing and reconstruction filtering for composite (CVBS) or S-Video signals in standard definition digital TV (SDTV) applications. The circuit is designed to drive a 75Ω termination, common in video applications, with an overall gain of 1.


This application note describes a 5.25MHz, 3-Pole, Butterworth filter using a Sallen-Key realization. It has gain of 2V/V, for driving a 75Ω back-terminated coax to an overall gain of 1. Such filters are used for video reconstruction of RGB and component video (Y, Pb, Pr) signals following a DAC to remove the higher frequency replicas of the signal, and as an anti-aliasing filter before an ADC.