A Power-Efficient Noise Suppression Technique Using Signal-Nulled Feedback for Low-Noise Wideband Amplifiers

The design of wideband amplifiers suffers from an essential tradeoff between noise and power consumption. This brief presents a power-efficient noise-suppression technique that excludes the signal from a noise-suppression loop by nulling the signal swing in transconductance cells. Once the loop is with less concern on signal linearity, the power constraint on the loop gain stage can be greatly relaxed. Two test circuits have successfully verified this technique. One is an radio-frequency low-noise amplifier (LNA) with the noise figure improved from 5 to 4 dB. The other is a baseband variable-gain amplifier (VGA) with an 11-dB noise reduction. The power overheads for applying the technique in the LNA and the VGA are 0.56 and 0.19 mW, respectively.