DIFFERENTIAL TERMINATION WITH AUTOMATIC COMMON-MODE TERMINATION VOLTAGE GENERATING CIRCUIT AND ATTENUATOR CIRCUIT NETWORK

摘要

PROBLEM TO BE SOLVED: To make direct current zero at an input node of a circuit network 60 and optimize a dynamic range of a differential amplifier 88. SOLUTION: A differential termination and an attenuator circuit network 60 have an automatic termination voltage generating circuit 61, and first and second termination resistors 68 and 70 are parallely connected to corresponding resistive attenuator circuits 84 and 86. A monitor circuit 66 is connected to an input node of the circuit network 60 and generates an output voltage indicating a combination of a direct current common-mode voltage VCMand a variable termination voltage VTERMat the input node. A control circuit 80 generates a scale-adjusted termination voltage VT, a compensation voltage VA, and a corresponding drive current through the use of the variable termination voltage VTERMand an output signal VIof the monitor circuit, and they optimize a dynamic range of the differential amplifier 88. The automatic termination voltage generating circuit 61 automatically adjusts the variable termination voltage VTERMin such a way as to be matched with a direct current common-mode input voltage and makes direct current zero at the input node. COPYRIGHT: (C)2006,JPO&NCIPI