Patent ID: 6621346
Filing Date: 2003-09-16
Classification: H04B,H04L

Abstract:
A modem, comprising:a host interface; a digital transceiver function coupled to the host interface; a line driver, for driving and receiving analog signals over a telephone facility; and an analog front end circuit, comprising: a digital interface, for communication of digital signals to the digital transceiver function; an analog-to-digital converter, having an output coupled to the digital interface, and having an input; and a programmable gain amplifier, having a signal input coupled to the line driver, having an output coupled to the analog-to-digital converter, and comprising: an operational amplifier having an input and an output; a plurality of input resistors, connected in series between the signal input and the input of the operational amplifier; a plurality of gain switches, each having a conduction path connected between an associated pair of the plurality of input resistors and the input of the operational amplifier; a plurality of matching resistors, connected in series between the signal input and a reference voltage; and a plurality of matching switches, each having a conduction path connected between an associated pair of the plurality of matching resistors and the reference voltage, and each of the plurality of matching switches associated with one of the plurality of gain switches so that the state of each of the plurality of matching switches corresponds to the state of its associated one of the plurality of gain switches.