A CMOS dB-linear RF VGA for SAW-less WEDGE transmitters

A CMOS dB-linear RF variable gain amplifier (VGA) that can provide a variable gain of 25-dB is implemented. The 25-dB of this range is achieved by a dB-linear V-I converter, which includes current limiting circuitry to reduce the gain variation due to process and temperature at maximum and minimum output power levels. The circuits are designed in a 0.13-um RF CMOS process. The measurement results demonstrate -45 dBc ACLR, -165-dBc/Hz Rx-band noise at 5-dBm output power and 25-dB dynamic gain control range in UMTS band for WCDMA. The RF VGA consumes 30-mA of current at maximum gain from a 1.8-V supply.