US4236801A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Exposure factor switching circuit
Assignee: Pentax Corp
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Filing: 1979-02-15
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Granted: 1980-12-02
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Expires: 1999-02-15
Abstract
Abstract An exposure factor switching circuit in a camera with an exposure control circuit having an emitter follower transistor adapted to apply a voltage through at least one transistor driven by a current flowing in the emitter thereof. A time constant circuit is adapted to control a shutter control magnet with an integration voltage due to a collector current of another transistor to the base of which the output of the emitter follower transistor is applied. A bias current supply circuit is employed having a plurality of transistors one of which is provided with a switch connected to the emitter thereof. The switch is operated to selectively activate the plurality of transistors to vary the emitter current of the emitter follower transistor.
Inventors
- 👤 Satoshi Takami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 02:21
CPC Classifications
G; G03; G03B; G03B9/00; G03B9/58; G03B9/62
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
140 words
For an exposure factor switching circuit for a camera with an exposure control circuit having an emitter follower transistor applying a voltage through at least one transistor which is driven by a current flowing in the emitter thereof, a time constant circuit controlling a shutter control magnet with an integration voltage due to a collector current of a second transistor, the output of said emitter follower transistor being applied to the base of said second transistor, the improvement comprising; a bias current supplying circuit comprising a plurality of transistors, one transistor of said plurality of transistors being emitter coupled to an exposure factor switch, said bias current supply coupled to the emitter of said emitter follow transistor, and wherein said switch is operated to selectively activate said plurality of transistors to vary the emitter current of said emitter follower transistor.
Claim 2
Dependent Claim
140 words
For an exposure factor switching circuit for a camera with an exposure control circuit having an emitter follower transistor applying a voltage through at least one transistor which is driven by a current flowing in the emitter thereof, a time constant circuit controlling a shutter control magnet with an integration voltage due to a collector current of a second transistor, the output of said emitter follower transistor being applied to the base of said second transistor, the improvement comprising; a bias current supplying circuit comprising a plurality of transistors, one transistor of said plurality of transistors being emitter coupled to an exposure factor switch, said bias current supply coupled to the emitter of said emitter follow transistor, and wherein said switch is operated to selectively activate said plurality of transistors to vary the emitter current of said emitter follower transistor.
Claim 3
Dependent Claim
39 words
The circuit of claim 1 wherein said bias current supply circuit further comprises a constant current source coupled to said plurality of transistors, and an output transistor having its collector coupled to the emitter of said emitter follower transistor.
Claim 4
Dependent Claim
38 words
The circuit of claim 2 wherein the plurality of transistors of said bias current supplying circuit comprises a plurality of diode connected transistors, said diode connected transistors having their collectors coupled to the base of said output transistor.
Claim 5
Dependent Claim
24 words
The circuit of claim 3 wherein said output transistor and said diode connected transistors have substantially equal base-emitter voltage vs collector current value characteristics.
Claim 6
Dependent Claim
134 words
For an exposure factor switching circuit for a camera with an exposure control circuit having an emitter follower transistor applying a voltage through at least one transistor which is driven by a current flowing in the emitter thereof, a time constant circuit controlling a shutter control magnet with an integration voltage due to a collector current of a second transistor, the output of said emitter follower transistor being applied to the base of said second transistor, the improvement comprising; a bias current supplying circuit comprising a multi-emitter transistor, one emitter of which is coupled to an exposure factor switch, said bias current supply coupled to the emitter of said emitter follow transistor, and wherein said switch is operated to selectively activate said multi-emitter transistor to vary the emitter current of said emitter follower transistor.
Claim 7
Dependent Claim
134 words
For an exposure factor switching circuit for a camera with an exposure control circuit having an emitter follower transistor applying a voltage through at least one transistor which is driven by a current flowing in the emitter thereof, a time constant circuit controlling a shutter control magnet with an integration voltage due to a collector current of a second transistor, the output of said emitter follower transistor being applied to the base of said second transistor, the improvement comprising; a bias current supplying circuit comprising a multi-emitter transistor, one emitter of which is coupled to an exposure factor switch, said bias current supply coupled to the emitter of said emitter follow transistor, and wherein said switch is operated to selectively activate said multi-emitter transistor to vary the emitter current of said emitter follower transistor.
Claim 8
Dependent Claim
23 words
The circuit of claim 5 wherein said multi-emitter transistor and said output transistor have substantially equal base-emitter voltage vs collector current value characteristics.
Claim 9
Dependent Claim
64 words
The circuit of claims 1, 3 or 5 wherein said time circuit comprises a capacitor in a parallel circuit with a synchronization switch, the collector of said second transistor being coupled to said parallel circuit and a comparator, said collector of said second transistor being coupled to one input of said comparator, and a voltage source coupled to the other input of said comparator.
Claim 10
Dependent Claim
22 words
The circuit of claim 7 wherein said synchronization switch is opened with the initiation of opening of a shutter in said camera.
Claim 11
Dependent Claim
36 words
The circuit of claims 1, 3 or 5 wherein said exposure factor switch reduces the current output of said bias current supplying circuit to one half the normal output when said exposure factor switch is closed.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-12-02 | 1984-06-02 | 1984-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-12-02 | 1988-06-02 | 1988-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-12-02 | 1992-06-02 | 1992-12-02 | $7700.00 | Window Closed / Lapsed |