A low-power low-noise accurate linear-in-dB variable gain amplifier with 500 MHz bandwidth

CDMA systems require variable gain amplifiers (VGAs) with wide dynamic range and wide frequency range in both transmitter (TX) and receiver (RX). A linear-in-dB variable-gain function is preferred in the VGAs, because a variable-gain range >80 dB is required. A variable-gain range <70 dB is preferable for VGAs in the IF stage in view of the desirability of realizing low noise and low distortion with reasonable power dissipation. In practice, a part of the required variable gain range (/spl sim/20 dB) is assigned to the RF stage.