Generalized Design Equations for Class-E Power Amplifiers with Finite DC Feed Inductance

In literature, it is widely accepted that the design of class-E power amplifier (PA) with finite dc feed inductance requires a long iterative solution procedure. To avoid such iterative solution methods, analytical design equations should be known. The problem associated with the finite dc feed inductance class-E PA is usually ascribed to the fact that the circuit element values are transcendental functions of the input parameters which is assumed to prevent the derivation of exact or fully analytical design equations. Using a proper analytical method, exact design solutions for class-E PA with any inductor value can however be derived. A mathematically exact analysis of the idealized class-E PA with finite dc feed inductance has been done and analytical expressions showing the relation between the circuit elements and the input parameters are found. These analytical expressions have been simplified to obtain explicit, relatively simple design equations. In this paper, it presents these relatively simple design equations. Using these design equations, class-E PA with finite dc feed inductance can be designed without iterative design procedures. The current paper discusses these simplified versions of the exact solution of general class-E PA with finite dc feed inductance, and discusses some implications of these design equations

I. Introduction

Since it's introduction [1] many aspects of the Class-E power amplifier has been extensively studied [2]–[9]. One such aspect is the Class-E operation with a finite dc-feed inductance. It is well-known that using finite dc feed inductance instead of an RF-choke in a Class-E PA has significant benefits [5], [8], [9], including: •

a reduction in overall size and cost

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a higher load resistance, which typically results in a more efficient output matching network [8]

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a possible reduction in the required supply voltage, which might enable the implementation of the Class-E PA in low-voltage technologies.

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larger switch parallel capacitor (Fig. 1) for the same supply voltage, output power and load. This enables higher frequency of operation.