Hitachi, Ltd.

Masatoshi Nakasu

Tetsuo Iijima

Minoru Suda

Atsushi Fujiki

Kazuaki Ohsawa

Nobuo Tsukagoshi

This semiconductor integrated circuit is constituted by any one of a p-channel MOS transistor and an n-channel MOS transistor, and is connected between the control terminal and the common terminal so as to produce predetermined voltage. The comparing circuit is operated in response to a control voltage applied between the control terminal and the common terminal so as to compare the predetermined reference voltage with the current-detected voltage which is obtained from the current detecting circuit. The gate controlling MOS transistor controls a gate voltage of the power MOS transistor based upon the comparison output of the comparing circuit. Then, all of these structural members are formed on the same semiconductor substrate.

Semiconductor integrated circuit having a current control function

A power transistor device is provided which has a function of clamping the collector voltage to a stable level for a wide range of temperature variations. In the power transistor device, a plurality of pn junctions are formed to fabricate Zener diodes in the polycrystalline silicon film in the form of rings. The ring configuration of the Zener diodes eliminates an end at the pn junction and prevents the junction surface from being exposed, making it possible to use as a stable Zener voltage the dielectric strength characteristic of the pn junction having a very small temperature coefficient.

Power transistor device having collector voltage clamped to stable level

In a transistor where collector is connected to an inductive load and switching current flows, a Zener diode comprising structure of plural pn-junctions constituted in series form to a polysilicon is provided between collector and base. Further MOSFET is switch-controlled by control voltage formed based on Zener current flowing through the Zener diode, and current path in parallel form to the Zener diode is constituted. Since temperature characteristic coefficient of a Zener diode formed in a polysilicon film is very small, the reverse voltage generated in the inductive load can be set to stable voltage in spite of the temperature variation. Further the MOSFET is provided in parallel form, thereby relatively large ON-resistance value of the Zener diode can be decreased.

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Shibukawa, Japan

Masatoshi Nakasu