An intermediate frequency variable gain amplifier with 1.5 dB gain flatness and optimized layout in the 45-nm SOI technique

A high-performance intermediate frequency variable gain amplifier (IF-VGA) in a superheterodyne receiver is presented. This IF-AMP has a cascade structure of a two-stage cascode amplifier with inductance-capacitance (LC) load and a one-stage common-source amplifier. The circuit is implemented in GlobalFoundries 45-nm SOI technology. It has a maximum gain of 17.1 dB, a gain tuning range of 18.7 dB, a gain flatness of 1.5 dB across a 3-4 GHz frequency range, and a 7.1 dB stopband rejection for the out-of-band 700 MHz frequency component. An optimized layout of digitally controlled resistor and capacitor arrays is proposed to minimize parasitic capacitance.