A wideband inductorless LNA exploiting three-stage feedback and thermal noise canceling

Abstract

In inductorless wideband low-noise amplifier (LNA) design, input-matching is traded off with noise figure (NF). The common-source noise-canceling (CSNC) structure and the gyrator alleviate this trade-off, but the corresponding study is insufficient. This work combines the CSNC and gyrator and introduces a three-stage feedback loop to achieve high feedback gain while minimizing the added input capacitance. Hence, the trade-off between NF and input impedance matching is significantly released. Consequently, the lowest NF among inductorless LNAs was achieved, while an operation bandwidth of more than 3 GHz was obtained. Post-layout simulation results in 40 nm CMOS technology show that the circuit achieves an NF of 1.35 dB–1.7 dB while maintaining a wide operation bandwidth of 100 MHz to 3.46 GHz. As far as the author knows, this is the lowest NF inductorless LNAs have achieved. Furthermore, S21 of 10.9 dB and IIP3 (input third-order intercept point) of −5.6 dB m are obtained, and the circuit consumes 14.9 mW at a 1.2 V voltage supply. Being self-biased, the circuit core consumes only 0.0032 mm2 die area.