Patent US3793522A successfully refreshed from Google Patents.
US3793522A
Expired / Lapsed
US
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Temperature compensating circuits for photo-conductive cells
Assignee: US Philips Corp
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Filing: 1971-09-27
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Granted: 1974-02-19
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Expires: 1991-09-27
Abstract
Abstract A temperature compensating circuit for a photoconductive cell whose resistance R varies with temperature and whose responsivity is a function of cell resistance. The circuit includes a transistor connected to the cell to provide a constant bias voltage thereacross so as to provide compensation for an R2 resistance dependence of cell responsivity. A positive feedback circuit for the transistor controls the transistor conduction as a function of cell resistance to cause the transistor to change the level of the cell bias voltage to provide compensation for a resistance dependence of cell responsivity in excess of R2, and more specifically between R2 and R3.
Inventors
- 👤 P Coleby
- 👤 I Kampel
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:48
CPC Classifications
G; G05; G05F; G05F1/00; G05F1/10; G05F1/46; G05F1/56; G05F1/565; G05F1/567; G01; G01J; G01J1/00; G01J1/42; G01J1/44; H; H03; H03F; H03F3/00; H03F3/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
121 words
A temperature compensating circuit for a photo-conductive cell having a cell resistance R which varies as an inverse function of temperature and a responsivity which is a function of cell resistance, said circuit comprising, in combination with said cell, means coupled to said cell for producing an output voltage which is a function of signal current produced by photoconduction of the cell, means for biasing said output voltage producing means to provide compensation for an R2 resistance dependence of cell responsivity, and means responsive to a change in cell resistance due to a change in cell temperature for modifying the operation of the output voltage producing means so as to compensate for resistance dependence of cell responsivity in excess of R2.
Claim 2
Dependent Claim
121 words
A temperature compensating circuit for a photo-conductive cell having a cell resistance R which varies as an inverse function of temperature and a responsivity which is a function of cell resistance, said circuit comprising, in combination with said cell, means coupled to said cell for producing an output voltage which is a function of signal current produced by photoconduction of the cell, means for biasing said output voltage producing means to provide compensation for an R2 resistance dependence of cell responsivity, and means responsive to a change in cell resistance due to a change in cell temperature for modifying the operation of the output voltage producing means so as to compensate for resistance dependence of cell responsivity in excess of R2.
Claim 3
Dependent Claim
92 words
A temperature compensating circuit as claimed in claim 1 wherein said voltage producing means comprises an output transistor with its base connected to receive a bias voltage which provides the compensation for the R2 resistance dependence, and wherein said modifying means includes a positive feedback circuit for the transistor which derives a feedback voltage for controlling the conduction of the transistor as a function of cell resistance to cause the bias voltage at the transistor base to change to correct for changes of cell responsivity due to a change in cell resistance.
Claim 4
Dependent Claim
44 words
A temperature compensating circuit as claimed in claim 2, wherein said feedback circuit includes a further transistor which provides positive feedback to the base of said first mentioned transistor in response to increased conduction of the latter due to a decrease of cell resistance.
Claim 5
Dependent Claim
90 words
A temperature compensating circuit as claimed in claim 1, in which the photo-conductive cell is provided with a constant voltage bias to provide the compensation for said R2 resistance dependence and said voltage producing means comprises an amplifier stage, and means for applying to said amplifier stage a signal current sampled from the cell to produce said output voltage, said amplifier stage being connected in the circuit so as to have a self-adjusting gain in dependence on cell resistance to provide said compensation in excess of an R2 resistance dependence.
Claim 6
Dependent Claim
52 words
A temperature compensating circuit as claimed in claim 4, in which the gain of said amplifier stage is determined by the emitter resistance of an input transistor thereof which is connected in circuit so as to have an emitter current that is approximately equal to the bias current of the photo-conductive cell.
Claim 7
Dependent Claim
101 words
A temperature compensation circuit for a photo-conductive cell having a cell resistance R which varies inversely with temperature and a responsivity which is a function of at least the square of cell resistance, said circuit comprising, means including a transistor amplifier for applying a constant voltage bias across the cell so as to compensate for said square law resistance dependence of cell responsivity, and means responsive to a change in cell resistance due to a change in cell temperature for compensating any resistance dependence of cell responsivity in excess of the square of cell resistance and caused by said temperature change.
Claim 8
Dependent Claim
101 words
A temperature compensation circuit for a photo-conductive cell having a cell resistance R which varies inversely with temperature and a responsivity which is a function of at least the square of cell resistance, said circuit comprising, means including a transistor amplifier for applying a constant voltage bias across the cell so as to compensate for said square law resistance dependence of cell responsivity, and means responsive to a change in cell resistance due to a change in cell temperature for compensating any resistance dependence of cell responsivity in excess of the square of cell resistance and caused by said temperature change.
Claim 9
Dependent Claim
108 words
A temperature compensation circuit as claimed in claim 6 including means connection said cell to the emitter of the transistor and in series therewith across a source of supply voltage, means for applying a constant bias voltage to the base of the transistor of a value to provide compensation for the square power resistance dependence of the cell, and said compensating means comprises a second transistor connected to provide positive feedback to the base of the first transistor so as to cause the first transistor to change the cell bias voltage to correct for a change in cell responsivity due to a temperature inspired change in cell resistance.
Claim 10
Dependent Claim
105 words
A temperature compensation circuit as claimed in claim 6 including means connecting said cell to the emitter of the transistor and in series therewith across a source of supply voltage, means for applying a constant bias voltage to the base of the transistor of a value to provide compensation for the square power resistance dependence of the cell, and said compensating means comprises a second transistor connected in circuit so that its emitter current is approximately equal to the bias current in the photoconductive cell and its gain varies with the cell resistance to provide said compensation in excess of the square of cell resistance.
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) | 1977-02-18 | 1977-08-20 | 1978-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-18 | 1981-08-20 | 1982-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-18 | 1985-08-20 | 1986-02-19 | $7700.00 | Window Closed / Lapsed |