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his on-line tutorial reviews the operation of servo amplifiers used to drive DC and brushless motors. The tutorial begins with a discussion of the power regulating methods, leading to the two types, linear and pulse-width-modulated (PWM) amplifiers. The PWM amplifiers are much more common, whereas linear amplifiers are used with a power rating of less than 100 watts. Further discussed is the switching method. The two common approaches, the bipolar and unipolar methods, are presented with their relative merits.
The tutorial considers the two common configurations for power amplifiers: current mode and velocity mode. It presents the block diagram and a mathematical model for both. Finally, the tutorial reviews the commutation method for brushless motors and presents the voltage waveforms and their relationship to the Hall sensors.