A 380-MHz CMOS linear-in-dB signal-summing variable gain amplifier with gain compensation techniques for CDMA systems

A linear-in-dB signal-summing Variable Gain Amplifier (VGA) is fabricated in 0.25 /spl mu/m CMOS technology. Two gain compensation techniques are proposed in order to compensate the gain deviations due to the MOSFET characteristic which has a square-law characteristic or an exponential-law characteristic determined by its current density. Temperature compensation techniques are also proposed. A gain range of 80 dB, a gain error of within /spl plusmn/3 dB, an NF of 11 dB are obtained at 380 MHz by measurement.