Power supplies available today offer more than just a source of voltage or current. Devices called operational supplies can serve as sophisticated amplifiers giving a flat response from dc to 20 kHz. They also handle up to 400 W continuously. These attributes give the supplies control characteristics analogous to those of servoamplifiers.
There are differences between operational supplies and servoamplifiers, however. One difference is in power ratings. Servoamplifiers generally are rated on the basis of average power to a load, but operational supplies carrying the same rating actually provide more power because the specification applies to continuous power output.