Abstract: This self tuned ultrasonic generator system for driving a piezoelectric transducer has a phase lock loop circuit for automatically finding and maintaining optimum drive of the transducer over a frequency range of at least 25% of a specified center frequency, regardless of variations of load, temperature, and configurations of the transducer. The loop circuit employs a voltage controlled oscillator driving a switching amplifier which powers the transducer. The signal from the oscillator is fed to a digital phase detector which receives as another input a sample of the current driving the transducer such that a phase comparison voltage from the detector is 15 applied to and controls the voltage of the oscillator. Another current sample is applied to a power supply to control the power supplied to the switching amplifier.