I'm studying the Class-F amplifier in order to eventually design one.
I'm trying to figure out how a load like of a Class-F looks like, but didn't manage to find some clear information about it.
In Class C E and F, the bias is below the threshold voltage.
If the input signal gets high enough the output will show a pulse corresponding with the top of the input signal.
The quiescent point of Class F amplifiers must be close to the cutoff region in order to generate significant amount of harmonics. The class F bias is located a bit higher than that of Class B.
The bias points for different PA classes are shown in Fig. 18.
Because of their similar bias points, the drain waveforms of Class F are similar to those of Class B. With harmonic control, larger voltage is created in Class F with the current clipping at the same level as Class B.
Therefore, Class F amplifiers are also known as overdriven Class B amplifier. Fig. 19 shows the voltage and current waveform of overdriven Class B PA, whose top of voltage waveform is flattened out as that in class F PA.