InGaP/GaAs HBT Broadband Power Amplifier IC with 54.3% Fractional Bandwidth Based on Cascode Structure
This paper presents the development of a broadband two-stage cascode PAIC with a fractional bandwidth of 54.3% using a 2-µm InGaP/GaAs HBT process. The higher supply voltage of the cascode PA results in a lower current, which can be advantageous for broadband operation because of the lower impedance transformation ratio of the output matching network. According to bandwidth analysis based on the power and efficiency contours at the internal plane of the transistor, an optimized shunt inductor for a single L-section load matching network is proposed to increase the bandwidth of the cascode PA by compensating for the output capacitance. The proposed PAIC was designed and implemented for the frequency band from 1.55 to 2.65 GHz. Using an LTE signal with a PAPR of 7.5 dB and a signal bandwidth of 10 MHz, a power gain of more than 23.7 dB, PAE from 30.9 to 38.4%, and average output power from 26.7 to 27.7 dBm were obtained at a given ACLR of -30 dBc.