A receiver with in-band IIP3>20dBm, exploiting cancelling of OpAmp finite-gain-induced distortion via negative conductance

Abstract

Highly linear CMOS radio receivers increasingly exploit linear RF V-I conversion and passive down-mixing, followed by an OpAmp based Transimpedance Amplifier at baseband. Due to the finite OpAmp gain in wideband receivers operating with large signals, virtual ground is imperfect, inducing distortion currents. We propose to apply a negative conductance to cancel this distortion. In an RF receiver, this increases In-Band IIP3 from 9dBm to >20dBm, at the cost of 1.5dB extra NF and <;10% power penalty. In 1MHz bandwidth, a Spurious-Free Dynamic Range of 85dB is achieved at <;27mA up to 2GHz for 1.2V supply voltage.