A 0.4–3.3 GHz low-noise variable gain amplifier with 35 dB tuning range, 4.9 dB NF, and 40 dBm IIP2

Abstract

This work presents a low-noise variable gain amplifier (LNVGA) in which the IIP2 is very high, and the gain control is applied to improve the system dynamic range, even with the limitations of the CMOS technology. Two stages compose the LNVGA, a low-noise amplifier (LNA), that keeps the noise figure (NF) at low values, and a variable voltage attenuator (VVA), that provides the gain variation. We have applied on the VVA the phase cancellation technique, in which the addition of two out-of-phase signals controls the gain. This technique provides a large gain tuning range only if the paths of the two signalsto be added are well balanced; hence, a precise 180 degrees phase difference is required. In this desing we propose an active balun with small imbalance, which creates those signals. The LNVGA was implemented in 130 nm CMOS with a 1.2 V supply. The measurement results show a 35 dB gain tuning range, varying from 10 to -25 dB, a 4.9 dB minimum NF, a -10 dBm IIP3, and an IIP2 as high as +40 dBm.