Abstract: The a. c. power converter forms an electronic alternating voltage transformer for transforming an essentially sinousoidal input alternating voltage of a predetermined frequency, e.g. power line frequency, and a first voltage into a second voltage of the same frequency and essentially the same wave shape. A chopper circuit (52) is coupled between input terminals (50a, 50b) and the primary winding of a transformer (54), dimensioned for the operating frequency of the chopper, e.g. 50-150 kHz. A secondary of the transformer is coupled to a rectifier circuit (60) having two output connections, on each of which one of two unipolar voltages of opposite polarities appear. The output terminals of the rectifier circuit (60) are each coupled through a low-pass filter (73a, 73b) to alternately conductive electronic switches (64a, 64b) and to a first (62a) of two output terminals. The second output terminal (66b) is coupled to a common terminal, e.g. a transformer center tap (56) of the rectifier circuit.

Abstract: A method of manufacturing a p-n, n.sup.+-n or p.sup.+-p junction in a semiconducting material, introducing into said material ions of an impurity material by exposing a surface of said semiconductor to a liquid containing ions of said impurity material, applying a voltage across said semiconductor-liquid interface, said voltage having a polarity and magnitude such that said ions are accelerated and drawn into said semiconducting material without the formation of a deposit of said impurity material on said exposed surface being necessary.