A Servo Motor Drive is a digital amplifier used to power servo motors. It monitors feedback signals from the motor and continually adjusts for deviation from expected behavior. The servo amplifier receives a low energy command signal from a control system, amplifies the signal, and transmits electric current to the servo motor in order to produce motion proportional to the commanded signal. Typically the command signal represents a desired velocity, but can also represent a desired torque or position. A velocity sensor attached to the servo motor reports the motor's actual velocity back to the servo drive. The servo motor drive then compares the actual motor velocity with the commanded motor velocity. It then alters the voltage frequency to the motor so as to correct for any error in the velocity.