Video differential bus receiver using transconductance stage

摘要

A transconductance amplifier (30) provides a video output signal (S3) current directly proportional to the transconductance (gm) of the amplifier and to a difference between first (S1) and second (S2) differential video input signals supplies thereto. A pair (10,20) of buffer amplifiers couples the video input signals (S1,S2) to respective inputs (31,32) of the transconductance amplifier via respective diode switches (CR1,CR2) which provides Vber protection for the buffer transistors (Q1,Q2) and provides bus isolation under power down conditions. An output circuit (50) regulates the output voltage of the transconductance amplifier (30) at a substantially fixed voltage and converts the output signal current to an output signal voltage. Advantageously, the receiver provides very accurate signal gain control, unconditional stability, a wide common mode input voltage range, avoids the need for stand-by power and will not load the input bus under power-down conditions.