2.6 GHz GaN-HEMT Doherty power amplifier integrated circuit with 55.5% efficiency based on a compact load network

This paper presents a GaN-HEMT DPA IC based on a compact load network for LTE small cells. The gate widths of the transistors for the carrier and peaking amplifiers are optimized to have the same load impedance of 100 Ω. A shunt inductor is added to compensate for the output capacitor of each transistor with parallel resonance. A x-type high-pass impedance transformer based on lumped components is used to modulate the load impedance. Parallel inductors from the resonant circuit and the impedance transformer are merged for further simplification. As a result, only two inductors remain in the load network. For verification, a 2.6 GHz DPA IC with an on-chip load network and input matching networks was designed and fabricated using a 0.4 μm GaN-HEMT process. The DPA IC exhibited a peak output power of 43.9 dBm. For an LTE signal with a signal bandwidth of 10 MHz and a PAPR of 6.5 dB, a high drain efficiency of 55.5% with an ACLR of -30 dBc was obtained at an average output power of 37.4 dBm.