A 450MHz 14dB variable gain amplifier in 0.35um CMOS process

A fully differential CMOS variable gain amplifier (VGA) has been designed. According to this design, linearity variation is effectively reduced during the gain variation, which is the main advantage of the proposed circuit. The gain of the circuit varies from 0dB to 14dB, respect to the control voltage. The circuit operates in open loop with -3dB bandwidth greater than 450MHz. Due to the structure, the bandwidth is almost independent of the gain and remains constant over the gain variations. For output voltage swing of 400mv p-p, the total harmonic distortion (THD) in low gain steps is less than -60dB and in high gain steps is -64dB. Layout of the whole circuit occupies an area of 0.028mm² which is compact in comparison to other VGA circuits. According to the Simulation results for CSMC 0.35 standard process, the power consumption of whole circuit is about 27mw with a 3.3v power supply.