Efficient InGaP/GaAs HBT Differential Power Amplifier Using a New Adaptive Cross-Capacitor Bias Circuit for 6G FR3 Handset Applications

This paper presents a 7–8.5 GHz differential power amplifier (PA) using a new adaptive cross-capacitor bias circuit (ACB) for handset application. The ACB is implemented as an adaptively applicable input bias circuit, connecting the base to the opposite emitter node of the common-collector (CC) stage in the input bias circuit. By placing an ACB in PA, imbalanced input bias current of differential signals is balanced, resulting in improved efficiency and output power. The proposed differential PA is implemented in a 2-µm InGaP/GaAs heterojunction bipolar transistor (HBT) process. Using the continuous wave (CW) signal, the PA achieves a gain of 19–22 dB, a saturated output power of 33–34 dBm, and a peak power added efficiency (PAE) of 30–41% over 7–8.5 GHz. The PA with NR 100-MHz 64 QAM cyclic prefix (CP) signal having a peak-to-average power ratio (PAPR) of 9.6 dB achieves average output power of 27–28 dBm and PAE of 19% in error vector magnitude (EVM) of -25 dB.