Abstract: An apparatus for measuring power in a power circuit, comprising a pulse width modulator comprising an integrator, a comparator having hysteresis characteristic and connected to the output side of the integrator, and a feedback circuit for feeding the output of the comparator back to the input side of the integrator; and an analog switch. The voltage of the power circuit is applied to the input of the integrator of the modulator so as to be pulse width modulated. The current of the power circuit is applied to the analog switch. The output of the modulator is applied to the analog switch to turn on and off the analog switch and thereby multiply the voltage and current. The apparatus is comprised of electronic circuit and may be fabricated by integrated circuit techniques. Advantageously, the invention eliminates the necessity of using separate movable coils for measuring the power.