An MMIC low-distortion variable-gain amplifier using active feedback

A new low-distortion variable-gain amplifier (VGA) is proposed and analyzed. The gain of the VGA is controlled using the transconductance of a common-drain FET (CDF) in the negative feedback path. The analysis and prototype results indicate that the third-order intermodulation-distortion ratio is greatly improved at a high input power levels due to the CDF's unilateral characteristic and a reduction in the VGA's input impedance.<
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