A system for linearizing the output of a high power amplifier (HPA) designed to transmit an RF modulated signal includes in its transmit section a digital up-converter for processing baseband input signals and generating a desired digital RF waveform, T(s). The desired digital RF waveform T(s) is then fed to a digital predistorter circuit for producing a predistorted digital RF waveform P(s)T(s) which, as modified, may be applied via a high sampling speed high linearity digital to analog converter to the high power amplifier (HPA) to produce an output signal which is a linear function of the baseband input signal. The digital predistorter circuit may be of the adaptive type or of the predictive type. Circuits embodying the invention may include encoding circuitry for converting multi-bit signals to a serial stream of single-bit pulses for enabling simplification in the digital to analog conversion. In accordance with the invention, corrections for non-linearity of the HPA may be made directly on the RF waveform using ultra-high speed superconducting electronics (SCE) and decreasing the time delay between sensing a transmitted signal and generating a correcting (linearizing) signal.