This paper presents exact analysis of class DE amplifier for any conditions including outside optimum conditions. We give an analytical expression of waveform equations and initial values of current and voltage in the steady state. By using these analytical equations, switching voltage, output voltage and power conversion efficiency of class DE amplifier can be derived with few efforts. In this paper, we denote the steady state behaviors outside optimum conditions which occur by the variations of operating frequency and switch on duty ratio. The theoretical results show a quantitative agreement with the experimental ones, which denotes the validity of analytical equations.