A special electric amplifier used to power electric servo motors.

A servo drive receives a command signal from a control system, amplifies the signal, and transmits electric current to a servo motor in order to produce motion proportional to the command signal. Typically the command signal represents a desired velocity. A velocity sensor attached to the servo motor transmits the actual motor velocity to the servo drive. The servo drive continually compares the actual motor velocity with the commanded motor velocity to generate an output to the motor that will tend to correct any error in the velocity.

In a properly configured system, the servo motor rotates at a velocity that very closely approximates the velocity signal being received by the servo drive from the control system.