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This letter presents a power-combined BiCMOS power amplifier (PA) system using envelope-tracking (ET) to serve as a fully monolithic solution for high peak-to-average ratio (PAR) broadband signals. The system consists of two cascode unit PAs combined by an on-chip transformer and modulated by a single envelope modulator. Without needing predistortion, the maximum linear output power of 24.6 dBm/23.8 dBm/23.2 dBm can be achieved with overall power-added-efficiency (PAE) of 26%/24%/22.5% for the LTE 16QAM 5 MHz/LTE 16QAM 10 MHz/WiMAX 64QAM 5 MHz signals at 1.9 GHz. The proposed power-combined ET-PA is fabricated in the TSMC 0.35 μm SiGe BiCMOS technology.