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US 4,904,860 AGranted
Optical signal detection circuit with constant current sources
AssigneeClarion Co., Ltd.
InventorHiroyuki Okagaki
Life of this patent
Estimating the term…
Abstract
An optical signal detecting circuit is configured so that its detection sensitivity for detecting an optical signal received by a light receiving element is set by selecting desired values of fixed current sources I and I' and a desired current division ratio of independent PNP multicollector transistors Q1 and Q2 and so that its optical signal detecting hysteresis range is set by selecting a desired current ratio of I and I' or a desired current division ratio of the independent PNP multicollector transistors Q1 and Q2.
Claims10
An optical signal detecting circuit, comprising:
- first and second transistors which each have a base and a plurality of collectors, wherein a first of said collectors and said base of said first transistor are connected to each other and to a first constant current source, and wherein a first of said collectors and said base of said second transistor are connected to each other and to a second constant current source;
- a light receiving element having a first end connected to ground and a second end connected to a second of said collectors of each of said first and second transistors;
- a third transistor which has a base and a plurality of collectors, said base of said third transistor being connected to said second end of said light receiving element, and a first of said collectors of said third transistor being connected to said first collector of said second transistor;
- fourth and fifth transistors which each have an emitter, a base, and a collector, said emitter of said fifth transistor and said collector of said fourth transistor being respectively connected to ground and to a power source, said emitter of said fourth transistor being connected to said collector of said fifth transistor, said base of said fourth transistor being connected to a third of said collectors of said second transistor, and said base of said fifth transistor being connected to a second of said collectors of said third transistor;
- and
- a sixth transistor having a collector, an emitter, and a base which are respectively connected to an output terminal, to ground, and to said collector of said fifth transistor.
3 more elements
A circuit comprising:
- a first transistor having an emitter coupled to a first terminal, having first and second collectors, and having a base;
- a second transistor having an emitter coupled to said first terminal, having first and second collectors, and having a base;
- a first constant current source coupled at a first end to a second terminal and coupled at a second end to said base and said first collector of said first transistor;
- a third transistor having an emitter coupled to said first terminal, having a collector and having a base;
- a second constant current source coupled at a first end to said second terminal, and coupled at a second end to said base and said first collector of said second transistor and to said collector of said third transistor;
- a light sensitive element having a first end coupled to said second terminal and having a second end coupled to said base of said third transistor, to said second collector of said second transistor, and to said second collector of said first transistor;
- first means for creating a difference in electrical potential between said first and second terminals;
- and second means coupled to an output terminal and responsive to said third transistor being on and off for causing said output terminal to respectively have first and second electrical states.
5 more elements
Dependencies are inferred from the claim text.