6.2 Generalized Class-E Load Network with Finite de-Feed Inductance

In real practice, it is impossible to realize an RF choke with infinite impedance at the fundamental frequency and its harmonic components. Moreover, using a finite dc-feed inductance has an advantage of minimizing size, cost, and complexity of the overall circuit. The detailed approach to analyze the effect of a finite dc-feed inductance on the idealized Class-E mode with shunt capacitance and series filter was first described in 1987 [8]. It was based on the Laplace-transform technique to solve a second-order differential equation describing the behavior of a Class-E load network with finite dc-feed inductance. Later, this approach was extended to the load network with finite (Q _L-factor of the series filter and finite device saturation resistance [9, 10]. The obtained results can be summarized as follows [10]:

• For a smaller dc-feed inductance, smaller detuning of a series-tuned circuit is necessary, which is very attractive for radio-transmitter applications where the amplitudes of the two sidebands should not be substantially different.

• Using a small dc-feed inductance is attractive when both the dc voltage and load resistance are specified and higher output power is needed.

• Q _L-factor of a series filter affects the power-amplifier performance less when the dc-feed inductance is small.

• Maximum output power increases as a dc-feed inductance decreases for large values of (2 _L-factor and behaves oppositely for small values of (2 _L-factors.

• Device saturation resistance r _sat should be taken into account, especially when...