Abstract: An input decision circuit includes a comparator outputting either one of a high voltage or a low voltage on the basis of the result of a comparison between a reference voltage and an input voltage, a base voltage source acting as a base common to the reference voltage and the input voltage, a constant current source supplying a constant current to a constant current path from a DC power supply to the base voltage source, and a resistor inserted in the constant current path. A constant voltage is produced across the resistor for the reference voltage with the electric potential of the base voltage source acting as a base. This provides an input decision circuit in which a threshold voltage is hard to shift even when the driving voltage of the comparator or the electric potential of the ground acting as the base voltage source is varied.

Abstract: A gate drive device which can suppress the fluctuation of an internal power source voltage and output voltage, while reducing the number of parts by omitting a bypass capacitor connected in parallel with a semiconductor integrated circuit, is provided. The gate drive device drives the gate of an active element with a large input capacity, such as an IGBT or MOSFET, and includes a semiconductor integrated circuit. The semiconductor integrated circuit has an internal power source based on an external power source, such as a battery. The semiconductor integrated circuit incorporates a voltage drop suppressing circuit, configured so that, if an input external power source voltage momentarily drops below a minimum operating voltage, a drop of an internal power source voltage below the minimum operating voltage, and a sharp drop in a voltage output to the gate, are prevented by the voltage drop suppressing circuit.

Abstract: A gate drive device which can suppress the fluctuation of an internal power source voltage and output voltage, while reducing the number of parts by omitting a bypass capacitor connected in parallel with a semiconductor integrated circuit, is provided. The gate drive device drives the gate of an active element with a large input capacity, such as an IGBT or MOSFET, and includes a semiconductor integrated circuit. The semiconductor integrated circuit has an internal power source based on an external power source, such as a battery. The semiconductor integrated circuit incorporates a voltage drop suppressing circuit, configured so that, if an input external power source voltage momentarily drops below a minimum operating voltage, a drop of an internal power source voltage below the minimum operating voltage, and a sharp drop in a voltage output to the gate, are prevented by the voltage drop suppressing circuit.