An exact analytical approach to the design of a Class-E high frequency power amplifier is presented. The analysis will optimize the load network parameters at the output of the switching transistor, while accounting for harmonics injected into the circuit from the choke inductor, finite quality factor of the output load network, and an exponential decay of the drain/collector current during OFF state. Calculated power performances in terms of efficiency and Total Harmonic Distortion (THD) as a function of decay angle and finite choke inductance are presented.