A wideband CMOS VGA with dB-linear gain based on active feedback and negative capacitance

Abstract

In this paper, a low power and wideband variable gain amplifier (VGA) with dB-linear gain control characteristic is presented. This design contains three stages of differential amplifier. To achieve accurate dB-linear characteristic and broadband response, sub-threshold loads and negative capacitance are employed, respectively. In addition, active feedback structure is utilized to further extend the bandwidth. Implemented in an 180nm CMOS process, simulation results indicate that the proposed VGA achieves a gain control range of 34 dB, which ∼25 dB is dB-linear with ±1 dB gain error and 1.1 GHz bandwidth. The power consumption is only 0.7 mW from a 1.8 V supply.