LDMOS transistors are widely used in power amplifiers at microwave frequencies for commercial applications such as communication base-station transmitters. The output capacitance of the LDMOS transistor is also nonlinear, similar to a general MOSFET transistor. In [22]–[24], the output capacitance is measured, estimated, or modeled in the same way as the characteristic of the MOSFET transistor. In [25], the simple depletion capacitance model is defined for an LDMOS transistor, with the expression is just the same as in (1). It is reasonable to measure a class-E power amplifier designed with an LDMOS transistor to study the effects of nonlinear output capacitance and also to verify the proposed efficiency enhancement method.