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US4112346A Expired / Lapsed US ⏱️ 0.0 years remaining

Constant current circuit

Assignee: Hitachi Ltd
•
Filing: 1977-08-09
•
Granted: 1978-09-05
•
Expires: 1997-08-09
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Abstract

Abstract A constant current circuit includes two characteristic-correlated PNP transistors connected to a constant voltage source and having common-connected emitters and common-connected bases and an NPN transistor. A constant current is taken out of a collector of a first PNP transistor. A collector of a second PNP transistor is connected to a base of the NPN transistor and the common-connected emitters of the first and second PNP transistors is connected to a collector of the NPN transistor to form a negative feedback circuit in the first PNP transistor, whereby when a current gain of the second PNP transistor which is characteristic corelated to the first PNP transistor is high a large amount of feedback is applied and when the current gain is low a small amount of feedback is applied so that the magnitude of the output constant current taken from the collector of the first PNP transistor is adjusted.

Inventors

  • 👤 Michio Tokunaga
  • 👤 Ichiro Ohhinata
  • 👤 Shinzi Okuhara

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-01 06:53
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/56

Claims Analysis

Total Claims: 9
Claim 1
Independent Claim 63 words
A constant current circuit comprising: characteristic-correlated first and second PNP transistors having common-connected emitters and common-connected bases, and an NPN transistor whose base is connected to the collector of said second PNP transistor and whose collector is connected to said common-connected emitters of said first and second PNP transistors in which constant current is derived from the collector of said first PNP transistor.
Claim 2
Dependent Claim 63 words
A constant current circuit comprising: characteristic-correlated first and second PNP transistors having common-connected emitters and common-connected bases, and an NPN transistor whose base is connected to the collector of said second PNP transistor and whose collector is connected to said common-connected emitters of said first and second PNP transistors in which constant current is derived from the collector of said first PNP transistor.
Claim 3
Dependent Claim 22 words
A constant current circuit according to claim 1, wherein said first and second PNP transistors are formed by a multi-collector PNP transistor.
Claim 4
Dependent Claim 44 words
A constant current circuit according to claim 1, wherein a base resistor and an emitter resistor are connected to the base and the emitter, respectively, of said NPN transistor, the resistance of the base resistor being larger than the resistance of the emitter resistor.
Claim 5
Dependent Claim 19 words
A constant current circuit according to claim 1, wherein said NPN transistor comprises a pair of Darlington-connected NPN transistors.
Claim 6
Dependent Claim 19 words
A constant current circuit according to claim 2, wherein said NPN transistor comprises a pair of Darlington-connected NPN transistors.
Claim 7
Dependent Claim 19 words
A constant current circuit according to claim 3, wherein said NPN transistor comprises a pair of Darlington-connected NPN transistors.
Claim 8
Dependent Claim 61 words
A multi-output constant current circuit comprising: a multi-collector PNP transistor having at least three collectors; and an NPN transistor whose base is connected to one of the collectors of said PNP transistor and whose collector is connected to the emitter of said PNP transistor, in which a plurality of constant currents are derived from the remaining collectors of said PNP transistor.
Claim 9
Dependent Claim 61 words
A multi-output constant current circuit comprising: a multi-collector PNP transistor having at least three collectors; and an NPN transistor whose base is connected to one of the collectors of said PNP transistor and whose collector is connected to the emitter of said PNP transistor, in which a plurality of constant currents are derived from the remaining collectors of said PNP transistor.

References Cited (Backward Citations)

US3714543A Cited
JPS50157044A Cited
US4063120A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1981-09-04 1982-03-06 1982-09-05 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1985-09-04 1986-03-06 1986-09-05 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1989-09-04 1990-03-06 1990-09-05 $7700.00 Window Closed / Lapsed

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