A Wide-Swing Low-Noise Transconductance Amplifier and the Enabling of Large-Signal Handling Direct-Conversion Receivers

In this paper, the design of a wide-swing low-noise transconductance amplifier (LNTA) is presented in the context of passive mixer-based direct-conversion RF receivers, noting that the compression performance of such systems is limited by the initial voltage-to-current conversion. The proposed LNTA utilizes a stacked PMOS/NMOS common-gate configuration with its input common-mode voltage maintained by a class-AB operational transconductance amplifier (OTA). Linearization mechanisms and design procedures are explained both quantitatively and intuitively. Simulations of the LNTA at the typical corner, when ideally loaded, show an IIP3 of
$+{\hbox {32.8}}~{\hbox {dBm}}$
extrapolated at a
$+{\hbox {12.5}}~{\hbox {dBm}}$
/
$-{\hbox {16.5}}~{\hbox {dBm}}$
CW blocking condition and an out-of-band 1-dB desensitization point of
$+{\hbox {22}}~{\hbox {dBm}}$
. These results are also shown to qualitatively agree with those extracted from an analytical model of the LNTA.