Fujitsu Corporation

Yasushi Yasuda

Hiromu Enomoto

Akinori Tahara

Yoshiharu Mitono

Hitoshi Ohmichi

Taketo Imaizumi

Masao Kumagai

Yoshiki Shimauchi

Hiroshi Ohta

Electrostatical breakage of a semiconductor device, including an epitaxial layer and a buried layer thereunder, connected to an outer signal terminal, can be prevented by forming an impurity region in the epitaxial layer so as to form a PN junction between the buried layer and the impurity region. The impurity region is connected to a power source or ground.

Semiconductor device with PN junction isolation for TTL or ECL circuits

A logic circuit which reduces occurrence of breakdown of the pull-down transistor and pull-up transistor in the output stage when a high voltage is applied to the power supply line and ensures high voltage resistance. The logic circuit controls a pull-up transistor provided between a first power supply and an output terminal which turns ON and OFF in accordance with a collector voltage of a phase splitter transistor and controls the pull-down transistor provided between the second power supply and output terminal with an emitter voltage. Breakdown of the pull-down and pull-up transistors can be reduced and a high voltage resistance ensured by providing a protection circuit which discharges the base of the pull-down transistor and turns OFF the pull-down transistor by detecting when a voltage difference between the first power supply and the second power supply exceeds a specified value.

Logic circuit

A gate circuit used for controlling an interface circuit in a microcomputer system, including a first-stage gate circuit, a second-stage gate circuit, and a control device connected between the first-stage gate circuit and the second-stage gate circuit. The first-stage gate circuit outputs an inverted strobe signal to the interface circuit, and the second-stage gate circuit outputs a non-inverted strobe signal to the interface circuit. Although there is a time lag in the changeover timing of these strobe signals, this time lag is reduced by connected the diode between the first-stage gate circuit and the second-stage gate circuit.

Two-stage gate circuit providing inverted and non-inverted outputs

A semiconductor device such as a TTL-type integrated circuit device which has an input protection circuit for each inner circuit, e.g., each TT logic gate. The input protection circuit is formed on a semiconductor substrate of a first conductivity type, and includes a first impurity region having a second conductivity type connected to an external terminal and an island-shape formed on the semiconductor substrate surrounded by an isolation region having the first conductivity type. The device also includes a clamp diode formed on an electrode layer contacting with the first impurity region. The device further includes a PN junction type protection diode formed on a second impurity region having the first conductivity type; the protection diode crosses the first impurity region between the clamp diode and a portion of the first impurity region connected to the external terminal and reaches the isolation region. The reverse withstand voltage of the PN junction type protection diode is smaller than that of the clamp diode, thereby preventing excessive reverse current flow and avoiding permanent destruction of the clamp diode.

Semiconductor device

A level shift element is connected between a transistor (Tr.sub.5) which is used to determine a threshold level when the input voltage falls and a diode (D.sub.3) is connected between an input terminal and an output control transistor (Tr.sub.2) to discharge the base of the output control transistor. The level shift element comprises a diode connected in the forward direction or a resistor.

Schmitt trigger circuit

A fundamental logic circuit used, for example, in an electronic computer, comprising an output inverter transistor and a switching transistor which discharges a base charge stored in a storage capacitance in a base-emitter junction of the output inverter transistor when the output inverter transistor changes from the turned on condition to the turned off condition.

Logic circuit with improved switching

A Schmitt trigger circuit has an input-voltage hysteresis characteristic for reducing noise sensitivity and preventing oscillation. In its input stage there is a multi-emitter transistor, and in its output stage a second transistor. The multi-emitter transistor comprises a first emitter and a second emitter. The first emitter is associated with a switching operation in response to the input voltage applied to the base of the multi-emitter transistor. The second emitter is associated with the operation of drawing charges from the base of the second transistor through the base of the multi-emitter transistor to the ground. The use of the multi-emitter transistor prevents the input current from increasing greatly as the input voltage falls.

Schmitt trigger circuit with low input current

A structure and method for manufacturing semiconductor devices by the master slice method, in which various kinds of semiconductor devices are manufactured through utilization of a common master pattern and a plurality of different kinds of selective wiring patterns. A number of bipolar transistors each having plural emitter regions, is formed in a predetermined region, or portion, of a semiconductor substrate by employing a common master pattern, and the plural emitter regions of the respective bipolar transistors are selectively connected by the associated wiring patterns of each thereof to form corresponding bipolar transistors of different, predetermined D.C. characteristics. When manufacturing many different kinds of semiconductor devices by the master slice method, the area which would be wasted on the semiconductor substrate by prior art techniques is greatly reduced, thus providing for enhanced area efficiency.

Structure for and method of manufacturing a semiconductor device by the

A semiconductor device including a diode and a bipolar transistor which are connected to each other and formed in an isolated area of a semiconductor layer has a diffused region formed between a base region of the bipolar transistor and a formation region of the diode across the isolated area. The diffused region has the same conductivity type as that of the base region, so that a PNPN diode effect does not occur.

Growing community of inventors

Inagi, Japan

Yasushi Yasuda