A self-oscillating pulse-width modulator comprises an input, an output and a control loop. In the ceramic material firing kiln tool plate, the decrease of heat capacity and the reduction of costs can be achieved, a contact area with the article to be fired is decreased to improve outgassing, and the atmosphere can be made uniform to uniformly manufacture the fired article. These further include, reporting, for each of the counters in the ordered set, a lower bound for the associated one of the distinct categories, wherein the lower bound is based upon a value of the counter and the global decrement counter. The controllable semiconductor elements have interconnected control electrodes which are also coupled to a bias voltage source, for biasing said control electrodes at a reference voltage. The vacuum arc vapor deposition apparatus further includes a coil power source for reversing a coil current to be fed to the magnetic coils, and a control unit for controlling the coil power source to reverse the flowing direction of the coil current. When the address Address includes redundancy addresses P1 to P4 designating a word line WLa or a bit line BLc connected to a specific memory cell Cc, redundancy decoders 13-1 to 13-4 replace the specific memory cell Cc with a redundancy memory cell RCc connected to redundancy word lines RWL1 and RWL2 or redundancy bit lines RBL1 and RBL2.