The invention AC transistor is a semiconductor with bipolar character being suitable for continuous control of alternative electrical characteristics and for effective switching. The AC transistor having a simple layer construction is free of all disadvantages of thyristors, TRIAC-s, applied in multilayer diode technique. As the AC transistor – called ACT – works according to the theory of amplitude contraction and not to that of phase splitting while controlling it gives a continual voltage without wave form distortion, making unnecessary any impelled usage of expensive R–L–C filter elements in linear mood of operation. AC transistor can be used advantageously as an AC switching element with great power, too, and it can be controlled from an AC as well as from a DC network.
Using it as a controlling element, as ACT automatically controls itself, it would not need the complex controlling circuits applied in multilayer diode technique. While the most simple types of the invention ACT can be used mainly as adjustable rectifying diodes, its more complex types – by replacing the magnetic amplifier can be advantageously used for voltage stabilization of AC supply units, making possible to reduce significantly the stabilizator dimensions as well. However, the basic field of applying complex multilayer ACT is to transform alternative network voltage into reduced voltage, as electronic transformer it is highly suitable to replace the traditional inductive transformers.