A CMOS IF Variable Gain Amplifier with Exponential Gain Control

An intermediate frequency (IF) variable gain amplifier (VGA) with exponential gain control for a radio receiver is fabricated in 0.25-μm CMOS technology. The techniques to improve the bandwidth and to reduce temperature dependence of gain are described. The complete VGA is composed of two stages of linearized transconductance VGA and three stages of fixed gain amplifier (FGA). The complete VGA provides a continuous 10 dB to 76.5 dB gain control range, an IIP3 of −11.5 dBm and an NF of 15 dB at 40 MHz. key words: variable gain amplifier, VGA, linearized transconductance, linear-in-dB characteristics, exponential gain control, CMOS