INTEGRATED UPSTREAM AMPLIFIER FOR CABLE MODEMS AND CABLE SET-TOP BOXES

摘要

An upstream amplifier (107) is integrated on a substrate (142) with a digital-to-analog converter (DAC) (102) to form integrated circuit. In an embodiment, a low-pass filter (104) is also integrated on the substrate (142). The output signal level of the upstream amplifier(107) is controllable. In embodiments, fine adjustments are made to the output signal level of the upstream amplifier (107) by varying a bias current of the DAC (102). A software control bit is used to switch between a power-on mode of operation and a power-down mode of operation. The upstream amplifier (107) transmits in a burst mode. The power consumption of the upstream amplifier (107) scales with the amplifier's output signal level. A high degree of matching is attained between the positive and negative paths of the upstream amplifier (107). This provides high immunity from common-mode disturbances such as substrate noise, clock spurs, and glitches caused by a gain change.