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 + 32.8 dBm extrapolated at +12.5 dBm/-16.5 dBm CW blocking condition and an out-of-band 1-dB desensitization point of +22 dBm. These results are also shown to qualitatively agree with those extracted from an analytical model of the LNTA.
© 2012 IEEE. Manuscript received September 06, 2010; revised January 15, 2011; accepted June 16, 2011. Date of publication August 12, 2011; date of current version January 11, 2012. The authors would like to thank an anonymous reviewer for pointing out the effect of feedback of the input device r_o on the CG LNTA NF.