A 270 MHz, 1 Vpk-pk, Low-Distortion Variable Gain Amplifier in a 0.35 m CMOS Process
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A fully balanced CMOS Variable Gain Amplifier (VGA) based on current-mode techniques suitable for high frequency applications and large signals is presented. The VGA consists of an analog multiplier, current gain stages, and resistive loads. A frequency compensation scheme based on a capacitive feed-forward technique increases the bandwidth by more than 60%. Common-Mode Feed-Forward (CMFF) techniques are used to minimize dc offsets. The gain can be programmed from 0 to 42 dB with -3 dB bandwidth greater than 270 MHz; a gain calibration scheme for precise gain control applications is included. The Third Harmonic Distortion (HD3) is less than -55 dB for differential input and output voltages of 1 Vpk-pk. The VGA was fabricated in a standard 0.35 m CMOS process, and consumes around 54 mW from a single power supply of 2.7 V.
