Certain aspects of the present disclosure provide an amplifier. The amplifier generally includes an amplifier core circuit configured to amplify a radio frequency signal and having a first output and a second output; a transformer coupled to the amplifier core circuit, the transformer having a primary winding and a secondary winding, the primary winding being coupled to the first output and the second output of the amplifier core circuit, the secondary winding being coupled to an output node of the amplifier; and a variable resistance circuit coupled in parallel with the primary winding.