Requirements for Test Automation

A power circuit having an output stage which includes voltage followers. The power circuit comprises first and second switching elements, respectively, connected between two voltage sources. A first comparator is provided to compare an input voltage with the output voltage of a voltage follower associated with the input voltage, and turn on the first switching element if the output voltage exceeds the input voltage. In addition, a second comparator is provided to compare the output voltage with a reference voltage to turn on the second switching element if the output voltage becomes lower than the reference voltage. A reference voltage circuit changes the value of the reference voltage depending on the output of the second comparator.