Wideband 70dB CMOS digital variable gain amplifier design for DVB-T receiver's AGC

摘要

This paper presents a novel VGA (variable gain amplifier) design which is applied in the AGC (automatic gain control) loop of DVB-T receivers. A total of three tunable gain stages are cascaded to provide a 70 dB dynamic range. Each gain stage is based on a DVGA (digital variable gain amplifier) which is composed of a plurality of GB (gain block) and a fully differential degeneration amplifier (FDDA). The GB are digitally controlled current mirrors which are used to determine the gain of the DVGA. A CMFB (common-mode feedback) circuitry is used to stabilize the FDDA. The bandwidth of the proposed design verified by HSPICE post-layout simulations is better than 95 MHz at every PVT corner which is sufficient for the DVB-T IF mixed-signal processing.