A temperature stable CMOS variable gain amplifier with 80-dB linearly controlled gain range

摘要

An IF variable gain amplifier (VGA) with a quadrature demodulator (QDEM) is fabricated in a 0.25-μm CMOS technology. In order to avoid the temperature dependence of the gain control characteristic, a master-slave control technique is adopted to the exponential voltage-to-current converters using MOS transistors biased in a subthreshold exponential region. Moreover, the VGA uses both a square-law region amplifier and an exponential region amplifier to obtain the wide gain control range. The experimental results show that the prototype chip achieves an 80dB linearly controlled gain range with 2.5 V supply voltage.