Abstract: A H-switch circuit is disclosed for rotationally driving a DC motor in a forward or reverse direction. The H-switch circuit comprises overcurrent-detecting circuits for four output transistors, which are respectively provided in order to detect the output transistor having an overcurrent, a circuit for generating an output signal upon detecting an overcurrent an integrating circuit controlled to be in a charge or discharge state according to the output signal representative of an overcurrent condition, and a circuit for turning off the output transistors when the integrating circuit is in the charge state and setting the integrating circuit to a discharge state. The charge and discharge operations of the integrating circuit are intermittently repeated until the overcurrent condition of the output transistor ends.

Abstract: A method for forming a Bi-CMOS structure, wherein a vertical npn transistor and CMOS transistors are formed on a single semiconductor substrate, is disclosed. After forming a p-type epitaxial silicon layer on a p-type silicon substrate with a plurality of n.sup.+ -type buried layers therein, n-type wells are formed to extend to the n.sup.+ -type buried layers. Selective oxidation is performed to form field oxide films so as to define an n-type element region for the npn transistor, an n-type element region for the p-channel MOS transistor, and a p-type element region for the n-channel MOS transistor. An oxide film as a gate oxide film for the CMOS is formed on the surfaces of all the element regions. After forming a p-type active base region of the npn transistor by ion-implantation of boron, an emitter electrode comprising an arsenic-doped polysilicon layer is formed in contact with the p-type active base region.