Abstract: For use in a gas sensor, an integrated gas sensitive unit comprises, on a single principal surface, a gas sensitive semiconductor element and a first resistor member connected to the element in series for deriving an electrical signal from the element. Both of the element and the first resistor member may be formed by the thick-film integration technique. A heating wire may be attached to the back surface opposite to the principal surface. A combination of secnd and third resistor members may be electrically connected to the series connection in parallel with the second and the third resistor members brought into electrical contact with the element and the first resistor member, respectively, to form a bridge circuit. The combination may be formed on the principal surface together with the series connection or separated from the series connection. Preferably, the first or the second resistor member has the same temperature dependency as the element when the heating wire is attached to the bridge circuit.

Abstract: A semiconductor (preferably a thyristor) switch has characteristics that can be represented by an equivalent circuit including an interconnected pair of opposite conductive types of transistors. The base terminals of these transistors represent anode and cathode gate electrodes of the thyristors. An amplifier which is free from erroneous actions due to the impression of a transitional voltage is connected to an electrode of the thyristor, which corresponds to the base terminal of an equivalent transistor of a first conductive type, in order to supply a gate current. A resistor across the base-emitter junction of an equivalent transistor of a second conductive type has a sufficiently low-resistance value to satisfy a predetermined dv/dt-bearing capacity. Therefore, a sustaining gate current is provided responsive to an amplification of the input to the amplifying means.