Fast frequency tracking control for radiofrequency power amplifiers with rapidly changing plasma loads

A radiofrequency power amplifier for a plasma processing system, comprising:

• a switching transistor having a drain terminal, a source terminal, and a gate, the source terminal electrically connected to a reference ground potential;
• a direct current power supply electrically connected to the drain terminal of the switching transistor;
• an impedance matching network electrically connected between the drain terminal of the switching transistor and a coil of the plasma processing system;
• an electrical parameter measurement device disposed to measure an electrical parameter related to the coil;
• and
• a phase delay module having an input electrically connected to receive a switching feedback signal from the electrical parameter measurement device, the phase delay module configured to apply a phase adjustment to the switching feedback signal to generate a switching control signal, the phase delay module having an output electrically connected to the gate of the switching transistor, the phase delay module configured to convey the switching control signal through the output of the phase delay module to the gate of the switching transistor.