0.2–4.35 GHz highly linear CMOS balun-LNA with substrate noise optimization Dong Huang 1 • Weiqiang Qian 1 • Mehdi Khan 1 • Shengxi Diao 1 • Fujiang Lin 1 Received: 19 January 2015 / Revised: 28 March 2015 / Accepted: 31 March 2015 / Published online: 23 April 2015 Ó Springer Science+Business Media New York 2015 Abstract A wideband CG–CS-based balun-LNA is pro- posed, with high linearity (IIP2 and IIP3) for multi-stan- dard radio applications. By taking advantage of the common-gate transistor’s noise and distortion cancellation property in CG–CS-based balun topology, this balun-LNA just focuses on CS-stage’s noise and linearity improve- ment. Post-distortion technique with a p-MOSFET as auxiliary transistor is adopted to suppress the 2nd and 3rd nonlinear terms of the main transistor in CS-stage, and then across 0.2–4.35 GHz, above 34 dBm IIP2 and 7.5 dBm IIP3 with typical process corner is achieved. In addition, in order to reduce the considerable substrate noise from the main transistor in CS-stage, a large resistor is connected between its bulk and source terminal, which reduces the substrate noise contribution from 7.68 to 0.2 % and im- proves the noise figure (NF) at 1 GHz about 0.38 dB. This balun-LNA was designed in 0.18-lm CMOS, operates from 0.2 to 4.35 GHz, and dissipates 17.8 mW with 1.5-V supply. With typical process corner, this amplifier provides 17.2-dB maximum voltage gain and 2.5–3.2 dB NF. Keywords Balun  LNA  Post-distortion  High linearity  Substrate noise  Noise optimization 1 Introduction Recently, in order to support multiple standards and fea- tures on a single chip, the research on multi-standard radio receivers has drawn much attention. The low noise am- plifier (LNA) is the first active block in the receiving chain and plays an important role in multi-standard receivers’ performance. In contrast to a multi-LNAs solution, a single wideband LNA is preferable in terms of flexibility, area, power and cost, but its performance like linearity (both IIP2 and IIP3 [1]) must be good enough to reduce signals’ mutual interference, due to the concurrent reception of unfiltered multiband signals. On the other hand, differential signal in receivers is preferable, due to its immunity to supply and substrate noise, and ability to reduce the 2nd- order distortion. But a balun is needed to convert the sin- gle-ended RF signal from antennas into differential signal. Nowadays, active balun is preferred in order to save area and reduce cost [2]. In these years, many balun-LNAs [9–13] combining the balun and LNA functionality into a single integrated cir- cuits for wideband receiver front-ends have been pub- lished, which can save I/O pins and afford high gain and low noise. The most familiar balun-LNA is the one based on CG–CS topology [2], which is benefited from the property of noise and distortion cancellation. As shown in Fig. 1, the noise and nonlinear distortion from common- gate transistor are output in common mode and cancelled when the two-side output are well balanced. Thus, this balun-LNA just needs to care about the CS-stage’s noise and linearity optimization. As is known, by enlarging the common-source transistor, this balun-LNA’s noise perfor- mance can be improved, but this method is invalid for linearity improvement. In order to obtain high linearity, [2] biases the common-source transistor in a narrow region & Fujiang Lin linfj@ustc.edu.cn Dong Huang hxd82@mail.ustc.edu.cn Shengxi Diao diaosxi@ustc.edu.cn 1 Department of Electronic Science and Technology, University of Science and Technology of China (USTC), Hefei 230027, Anhui, People’s Republic of China 123 Analog Integr Circ Sig Process (2015) 83:285–293 DOI 10.1007/s10470-015-0533-z