A programmable gain amplifier buffer design for video applications

A programmable gain amplifier (PGA) for video decoder application is presented: 16 linear gain steps from 1.35 to 5.4, 2.5 Vpp output swing, better than -55 dB THD (1 MHz, 2.5 Vpp) for 10 pF loading and 3 V power supply. The programmability is implemented by switching on/off resistors through a low distortion switching scheme. In this scheme, as the switches are symmetrically positioned at amplifier virtual ground, not only low distortion but also gain independent offset are achieved.