A complete audio power amplifier, with two channels and a power rating on the order of tens of watts, can be put into a small integrated circuit package, needing only a few external passive components to function. Another important application for active-mode amplifiers is in linear regulated power supplies, when an amplifier device is used as a voltage regulator to maintain load voltage at a desired setting. While such a power supply may be less energy efficient than a switched mode power supply, the simplicity of application makes them popular, especially in current ranges up to about one amp.