A 0.1 to 5GHz ultra-wide band single-to-differential CMOS LNA with output balancing for SDRs

Abstract

A 0.1-5GHz ultra-wide band (UWB) single-to-differential (S-to-D) CMOS LNA with differential imbalance correction is implemented as a part of a software defined radio (SDR) which supports multi-band and multi-standard. The proposed S-to-D LNA is composed of a S-to-D converter, a differential-to-single (D-to-S) voltage summer with inductive shunt peaking, a negative feedback network, and a differential output buffer with composite common-drain (CD) and common-source (CS) amplifiers. By feeding the single-ended output of the voltage summer to the input of the LNA through a feedback network, a wideband S-to-D LNA exploiting negative feedback is implemented. By adopting common-drain based inductive shunt peaking, the S-to-D LNA achieves a wider gain bandwidth. A differential output buffer composed of two CS and two CD amplifiers corrects the imbalance of the differential output of the S-to-D converter. The 3dB gain bandwidth of the proposed S-to-D LNA is above 5GHz and the NF is below 4dB from 100MHz to 5GHz. An average power gain of 18dB and an IIP3 of −8 ∼ −2dBm are obtained. The differential output of the proposed S-to-D LNA has a gain difference of less than 0.3dB, and a phase imbalance of lower than 3° from 0.1GHz to 5GHz.