An all CMOS 84dB-linear low-power variable gain amplifier

A new exponential approximation function is implemented into a variable gain amplifier (VGA). The newly proposed VGA topology provides low-power, small chip size, and wide control gain range. The VGA is fabricated in 0.18μm CMOS technology and measurements show a gain variation of more than 84dB in two cascaded stages, and 80dB-linear range with a linearity error of less than ±1dB. The PldB varies from -42dBm to -22dBm. The power dissipation is less than 3.6mA from 1.8V supply. The chip excluding bondpads occupies 0.4mm².