Allen-Bradley 8520-AA21 Servo Amplifier Module

The Allen-Bradley 8520-AA21 Servo Amplifier Module is a single-axis digital servo amplifier in the 9/SERIES CNC family, rated for 21 A to drive a servo motor in precision motion systems. It acts as the high-current output stage of the 8520 CNC servo system, translating PWM commands from the 8520 digital servo module into the drive signals that energize the motor, enabling accurate position, velocity, and torque control in CNC applications. Weighing 22.51 lb, the 8520-AA21 is a compact module designed for use on a single axis within classic AB CNC configurations. The model is listed as 8520-AA21 and is described as discontinued by the manufacturer, reflecting its status in the current catalog. Typical applications include milling, turning, and other CNC machine tools that rely on Allen-Bradley 9/SERIES servo control architecture for reliable servo performance.