A 60-dB 246-MHz CMOS variable gain amplifier for subsampling GSM receivers

A variable gain amplifier (VGA) is designed for a GSM subsampling receiver. The VGA is implemented in a 0.35-(mu)m CMOS process and approximately occupies 0.64 mm/sup 2/. It operates at an IF frequency of 246 MHz. The VGA provides a 60-dB digitally controlled gain range in 2-dB steps. The overall gain accuracy is less than 0.3 dB. The current is 9 mA at 3 V supply. The noise figure at maximum gain is 8.7 dB. The IIP3 is -4 dBm at minimum gain, while the OIP3 is -1 dBm at maximum gain. The group delay is 1.5 ns across 5-MHz bandwidth.