A Compact PA-LNA Bi-Directional Amplifier Using Transistor Switch Achieving High Integration in 40-nm LP CMOS

This paper proposes a design methodology for integrating the Power Amplifier (PA) and Low Noise Amplifier (LNA) into a single Bi-Directional Amplifier (BDA) to simultaneously achieve miniaturization and high integration in beamforming systems. The proposed BDA switches between PA and LNA operating modes using transistor switches and gate bias, thereby enabling bidirectional utilization that significantly reduces overall system complexity and size. Simulations based on a 40-nm LP CMOS process demonstrate a maximum gain of 19.9 dB, a saturated output power (P<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SAT</inf>) of 16.6 dBm, and a peak power-added efficiency (PAE) of 19% at 27 GHz in TX mode. At 25 GHz in RX mode, the BDA achieves a gain of 21.5 dB with a low noise figure of 3.1 dB. In addition, stable K-factor values are maintained when switching between TX/RX modes, and the amplifier exhibits excellent isolation performance that minimizes cross-mode interference. These results verify that the proposed BDA serves as an effective solution for next-generation millimeter-wave beamforming systems, fulfilling both high-output/low-noise performance and system miniaturization requirements.