In this work, a hybrid 5.7 GHz gallium-nitride high electron mobility transistor (GaN HEMT) transformer-based Doherty power amplifier (TBD PA) to support 40-MHz bandwidth (BW) long term evolution-advanced (LTE-A) applications is presented. A series-combining transformer is used to realize Doherty action instead of using conventional quarter-wave length impedance inverter to cover wide bandwidth modulation signals. Also the AM-PM distortion generated by the Doherty action is compensated with a varactor-based linearizer to gain better linearity. The proposed hybrid TBD PA is implemented using Cree's 6 W GaN HEMT bare die (CGHV1J006) and Semco's 7 layer PCB. The TBD PA is tested at 5.7 GHz carrier frequency and showing 43% peak PAE and 39.3 dBm maximum output power with continuous wave (CW) signal, −33 dBc CA E-UTRAACLR at 31.8 dBm output power with 40-MHz BW LTE-A Signal by using the fabricated linearizer.