To control a motor, a pulse width modulated signal from a computer is fed to a capacitor which stores each pulse as a voltage proportional to the width of the pulse, the capacitor being reset to zero by a leading edge reset circuit. The voltage on the capacitor is sampled by a sample/hold circuit the output of which is fed to a converter which converts the voltage signal to a frequency signal exponentially related to the voltage, and hence to the pulse width. The converter then powers a driver which drives the motor. The exponential relationship between the pulses and the signal fed to the motor permits a large variationin the frequency signal based on a small variation in pulse width and hence permits accurate control of the motor.