A 1.5–2.7 GHz 3-dB NF 32-dB Notch-Depth Channel-Selection Balun-LNA Employing Dual Feedback and Feedforward <i>N</i>-Path Filter Loops for Advanced Cellular Application

This paper presents a channel-selection (CH-SEL) balun-low-noise amplifier (LNA) with dual feedback (FB) and feedforward (FF) N-path filter loops for advanced cellular applications. The FB N-path filter loop exhibits high-Q radio frequency (RF) bandpass filter characteristics at the input and output of the LNA while performing input impedance matching. The FF N-path filter loop provides an adjustable sharp-notch characteristic via a gain- and phase-mismatch calibration. Therefore, the proposed CH-SEL balun-LNA employing dual N-path filter loops can effectively eliminate transmitter leakage signals and out-of-band blockers, thereby improving the overall linearity of the receiver through the filtering effect. Fabricated via a 65-nm CMOS process, the CH-SEL balun-LNA achieves a noise figure of 3 dB, a voltage gain of 26.6 dB, a blocker-rejection ratio of 32 dB, and an out-of-band input-referred third-order intercept point of 13.2 dBm. It consumes a bias current of 23.1 mA from a nominal supply voltage of 1 V. The active die area is 0.72 mm2.