US Patent 11437219 Frequency tuning for a matchless plasma source

Frequency tuning for a matchless plasma source is described. To perform the frequency tuning, current is measured at an output of an amplification circuit of the matchless plasma source after a change in a frequency of operation of the matchless plasma source. Upon determining that the current has increased with the change in the frequency of operation, the frequency of operation is further changed until the current has decreased. When the current has decreased, the changed frequency of operation is further modified to be an operational frequency. When the matchless plasma source operates at the operational frequency, the current at the output of the amplification circuit is maximized.