Wireless circuitry with low-noise peak detection

Abstract

An electronic device may include an antenna, a receiver, and a transmission line path that couples the antenna to the receiver. A peak detector may receive a radio-frequency signal from the transmission line path and may output a DC voltage indicative of a peak voltage level of the signal. The peak detector may include a pair of square law transistors having source-drain terminals coupled to an output of the peak detector. The peak detector may include a differential pair of transistors coupled between a power supply voltage and the output. The peak detector may include diode-connected transistors coupled between the source-drain terminals and gate terminals of the square law transistors. The diode-connected transistors may cause noise current to flow along feedback loop paths from the source-drain terminals onto the gate terminals of the square law transistors. This may remove noise from the output of the peak detector.