This paper describes about theoretical design of class D power amplifier. Amplifier is primarily intended for laboratory measurements, i.e. measuring of major parameters of amplifier operates in this class (frequency response, slew rate, aliasing etc.). Amplifier (oncoming laboratory module) uses PWM (Pulse Width Modulation) and is constructed from separate blocks for possibility of measuring key signals trough all the structure (triangle comparation wave, analog input signal, feedback signal, PWM signal from modulator, drivers and power transistors, output signal after recontruction filters). Laboratory module is determined for laboratory power supply of safe voltage and should be produce power of several tens of watts into usual load impe...