Fujitsu Corporation

Fujitsu Ten Limited

Fijitsu Limited

Masaharu Atsumi

Yoshiaki Sano

Satoru Kishimoto

A thyristor is preferably fabricated as a single thyristor device in an integrated circuit. The thyristor is made conductive by applying an ordinary gating voltage to the gate thereof. However, the thyristor can be kept in a conductive state, even though a current flowing through the anode and cathode thereof is stopped, if the current is restored to flow through it again within a predetermined short time after has stopped. The thyristor is composed of a first transistor and a second transistor (both of which are also used in a typical thyristor component) a third transistor which forms a Darlington connection with the second transistor, a resistor which is connected between the base and the emitter of the third transistor, and a capacitor which is connected between the base of the second transistor and the emitter of the third transistor.

Thyristor with 'on' protective circuit and darlington output stage

A constant-current source transistor, which exhibits a constant-current characteristic corresponding to the power source voltage of a sensor and is connected to an input signal terminal of an input circuit, such as a microprocessor. A first transistor is connected so that it may supply a current from the power source of the input circuit to the constant-current source transistor, and a second transistor is connected in parallel to the constant-current source transistor. When the signal level at the input signal terminal exceeds a predetermined value, the second transistor is turned ON to effect level control so the input signal level may not become excessively high and damage the input circuit.

One-terminal type level control circuit

A clamping transistor is connected to a signal input terminal of a signal processing circuit, such as a microprocessor, which operates on the output voltage from a stabilized power source circuit. When the output voltage from the stabilized power source circuit is below a predetermined value at the time of turning ON or OFF a power source switch, the clamping transistor is held in the ON state, thereby preventing the application of an input signal of a level higher than the power source voltage of the signal processing circuit, to the signal input terminal of the signal processing circuit.

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Kakogawa, Japan

Masaharu Atsumi