An electronic device may include wireless circuitry. The wireless circuitry may include at least a digital predistortion circuit, an upconversion circuit, and a load-line modulated amplifier circuit. The digital predistortion circuit can be configured to receive a reference baseband signal from one or more processors and to selectively output a predistorted version of the reference baseband signal. The upconversion circuit can be configured to receive a signal from the digital predistortion circuit and to output a radio-frequency signal. The load-line modulated amplifier circuit can be configured to amplify the radio-frequency signal. The load-line modulated amplifier circuit can include an adjustable load component. The adjustable load component can have a constant impedance when an instantaneous signal amplitude of the reference baseband signal is within a first range and can be tuned to have a varying impedance when the instantaneous signal amplitude of the reference baseband signal is within a second range.