Hitachi, Ltd.

Akisada Moriguchi

Teruhisa Azumaguchi

Kohei Ishizuka

Osamu Yumoto

Tamio Takeuchi

Masaya Nakata

Tsutomu Kohno

Hironori Saito

Junji Takeda

Masaharu Hata

Atushi Miura

Hiroki Irie

A constant-voltage power source circuit includes a first current mirror circuit having a diode and a first transistor and a second current mirror circuit having at least second and third transistors, which sets a current flowing to the first current mirror circuit to be substantially equal to a current flowing to the second mirror circuit, and provides the current flowing to the second current mirror circuit to a fourth transistor that determines an output voltage. With this arrangement, a current flowing to the current mirror circuits structured by the diode and transistors is determined by a forward characteristic of the diode, and this current becomes a constant current which is hardly affected by a variation of a power source voltage. When this current flows to the two current mirror circuits including transistors and then flows to the transistor which determines an output voltage, it is possible to hold a voltage between the base and the emitter of the transistor which determines an output voltage, at substantially a constant value without being affected by a variation of the power source voltage.

Low-constant voltage supply circuit

A light transmission module is disclosed, having a light receiving element module, in which a photodiode and a coupling portion between the photodiode and a first optical fiber are hermetically sealed, and a light emitting element module, in which a laser diode driven by an electric signal and a coupling portion between said laser diode and a second optical fiber are also hermetically sealed. A two-sided print board is provided, on the two sides of which electric circuits for a transmitting system and a receiving system are mounted. The electric circuits for the transmitting and receiving circuits are; isolated electrically from each other, and are sealed in one body by molds, and accommodated in cases, together with the light receiving element module and the light emitting element module.

Light transmission module

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Ome, Japan

Akisada Moriguchi