This instantaneously interruptible power source (I.sup.2 PS) produces a precise AC output voltage. The I.sup.2 PS can be built using only 7 power components, including an output capacitor. Moreover, currents applied thereto are unidirectional and independently developed. In the conventional switching power amplifier or uninterruptible power source, an output inductor continuously delivers a current to an output capacitor. A precise correction is simply impossible since, at the end of every switching cycle, the correction is either insufficient or continues while no longer required. This includes even most sophisticated class-D amplifiers. By contrast, the I.sup.2 PS can instantaneously interrupt the correction and become idle. Without transformation, the output voltage can exceed supply voltages. An inductive block comprises at least one inductor and/or transformer for providing a return voltage. A switch or switches selectively apply a DC supply voltage or voltages to the inductive block. A rectifier limits the return,voltage, e.g. to one supply voltage. Another switch or switches can be used for selectively applying the output voltage to the inductive block. The output capacitor provides the output voltage of the I.sup.2 PS.