An analysis is given for sub-optimum conditions of class E amplifier with a nonlinear shunt capacitance with a grading coefficient of 0.5 at any duty cycle. By exploiting sub-optimum class E operation, various amplifier parameters such as input voltage, operating frequency, output power, and load resistance can be set as design specifications. An example of a design procedure of the class E amplifier is given. The theoretical results were verified with Pspice simulation using SPICE MOSFET model