An Inductorless Low Power Wideband Push-Pull Balun LNA with Dual Stage Noise Cancelation andIIP2/IIP3 Linearity Modes for Sub-GHz Wireless Applications
In this paper, an inductorless common source (CS) - common gate (CG) complementary push-pull balun LNA is proposed for sub-GHz low power applications. A dual stage noise cancelation technique is proposed to reduce the noise figure (NF) of the circuit. To maximize the linearity performance, a tunable nMOS based source follower feedback in shunt to the CS stage is employed. Tunable feedback maximizes the IIP2 in the IIP2 mode while it maximizes the IIP3 in the IIP3 mode. The circuit operates in two power modes - low power mode (LPM) (1.2 V supply) and high linearity mode (HLM) (1.8 V supply). In the LPM , IIP2 performance is improved while IIP3 performance is limited by the third order output conductance non-linearity. In the HLM, both IIP2 and IIP3 performance is maximized. The circuit, implemented in 0.18µm RFCMOS process, achieves a maximum gain of 15.5 dB with minimum NF of 3.2 dB while maximum 3-dB bandwidth ranges from 65 MHz to 840 MHz. In the LPM, the maximum IIP2 and the maximum IIP3 are 48 dBm and 1.3 dBm respectively while in the HLM, the maximum IIP2 and the maximum IIP3 are 43 dBm and 8.3 dBm respectively. In LPM, it dissipates a maximum total power of 3.75 mW while in the HLM, it dissipates a maximum total power of 6.4 mW. To the authors’ best knowledge, the proposed balun LNA achieves the best linearity performance reported till date.