US3872329A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Radiation sensing circuit
Assignee: RCA Corp
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Filing: 1974-03-07
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Granted: 1975-03-18
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Expires: 1994-03-07
Abstract
Abstract A phototransistor provides an output current via a circuit node to a current path. An operational amplifier connected at its noninverting input terminal to ground and at its inverting input terminal to the node provides a feedback signal to the base of the phototransistor in a sense to establish the node at a virtual ground for maintaining the phototransistor output current equal to a fixed current withdrawn by the current path.
Inventors
- 👤 Iii George Bertram Dodson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:57
CPC Classifications
H; H03; H03F; H03F17/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
249 words
In combination: a circuit node; a radiation sensor having a control terminal to which a control signal may be applied for adjusting the radiation sensitivity of said sensor and having also an output current path connected to said node for supplying an output current thereto, said output current being proportional to the intensity of radiation applied to said sensor at a given control signal level applied to said control terminal; a second current path connected to said circuit node for withdrawing from said node a fixed current level, said second current path accepting the current supplied to said node by said output current path; circuit means for supplying said control signal to said sensor and for maintaining said circuit node at a given virtual reference voltage level, said circuit means including means responsive to any tendency for the current level in said output current path to change, for changing the value of the control signal in a sense to return the flow of current in said output current path to its original value; and low pass filter means for initially receiving said control signal produced by said circuit means, attenuating said control signal and applying the attenuated control signal to said sensor, said low pass filter means having a first and a second, higher, break frequency and providing minimum attenuation of said control signal at frequencies below said first break frequency and a fixed maximum value of attenuation of said control signal at frequencies above said second break frequency.
Claim 2
Dependent Claim
249 words
In combination: a circuit node; a radiation sensor having a control terminal to which a control signal may be applied for adjusting the radiation sensitivity of said sensor and having also an output current path connected to said node for supplying an output current thereto, said output current being proportional to the intensity of radiation applied to said sensor at a given control signal level applied to said control terminal; a second current path connected to said circuit node for withdrawing from said node a fixed current level, said second current path accepting the current supplied to said node by said output current path; circuit means for supplying said control signal to said sensor and for maintaining said circuit node at a given virtual reference voltage level, said circuit means including means responsive to any tendency for the current level in said output current path to change, for changing the value of the control signal in a sense to return the flow of current in said output current path to its original value; and low pass filter means for initially receiving said control signal produced by said circuit means, attenuating said control signal and applying the attenuated control signal to said sensor, said low pass filter means having a first and a second, higher, break frequency and providing minimum attenuation of said control signal at frequencies below said first break frequency and a fixed maximum value of attenuation of said control signal at frequencies above said second break frequency.
Claim 3
Dependent Claim
101 words
The combination recited in claim 1 wherein said radiation sensor comprises: a phototransistor having emitter, base and collector electrodes, said collector electrode for receiving a first operating potential, said base electrode for receiving said control signal from said low pass filter means, said emitter electrode for supplying said output current to said node whereby the collector-to-emitter voltage of said phototransistor is maintained equal to the potential difference between said first operating potential and the potential of said virtual reference voltage and the emitter current is maintained equal to said fixed current level withdrawn from said node by said second current path.
Claim 4
Dependent Claim
67 words
The combination recited in claim 2 wherein said circuit means comprises: a differential amplifier having an inverting input terminal, a non-inverting input terminal and an output terminal, said inverting input terminal being connected to Said node, said non-inverting input terminal being maintained at said given reference voltage level, said output terminal for producing said control signal and supplying said control signal to said low pass filter means.
Claim 5
Dependent Claim
64 words
The combination recited in claim 3 wherein said low pass filter means comprises: a circuit node; a first resistor connected between said output terminal of said differential amplifier and said node; a second resistor connected between said base electrode of said phototransistor and said node; and a third resistor and a capacitor connected in series between said node and a signal ground reference point.
Claim 6
Dependent Claim
55 words
The combination recited in claim 1 further comprising means in said low pass filter means for producing a band rejection filter response having said fixed maximum value of attenuation for control signal frequencies above said second break frequency and below a third break frequency, said third break frequency being higher than said second break frequency.
Claim 7
Dependent Claim
50 words
The combination recited in claim 3 wherein said second current path comprises: a terminal for receiving a second operating potential; and a further resistor connected between said terminal and said node, said first and second operating potentials being of opposite polarity taken with respect to said given reference voltage level.
Claim 8
Dependent Claim
152 words
In combination: a differential amplifier having inverting and non-inverting input terminals and an output terminal, said non-inverting terminal being maintained at a reference potential; first means for applying a bias signal of one sense to said inverting input terminal; radiation responsive means for applying a further bias signal of opposite sense to said inverting terminal, the magnitude of said further bias signal being representative of a radiation input signal and a control signal supplied to said radiation responsive means; and filter means for supplying said control signal to said radiation responsive means in response to an output signal produced at said output terminal of said differential amplifier said filter means having a first and a second, higher, break frequency and providing minimum attenuation of said control signal at frequencies below said first break frequency and a fixed maximum value of attenuation of said control signal at frequencies above said second break frequency.
Claim 9
Dependent Claim
152 words
In combination: a differential amplifier having inverting and non-inverting input terminals and an output terminal, said non-inverting terminal being maintained at a reference potential; first means for applying a bias signal of one sense to said inverting input terminal; radiation responsive means for applying a further bias signal of opposite sense to said inverting terminal, the magnitude of said further bias signal being representative of a radiation input signal and a control signal supplied to said radiation responsive means; and filter means for supplying said control signal to said radiation responsive means in response to an output signal produced at said output terminal of said differential amplifier said filter means having a first and a second, higher, break frequency and providing minimum attenuation of said control signal at frequencies below said first break frequency and a fixed maximum value of attenuation of said control signal at frequencies above said second break frequency.
Claim 10
Dependent Claim
37 words
The combination recited in claim 7 wherein said first means comprises: a first terminal for receiving a first operating potential; and a resistor connected between said first terminal and said inverting input terminal of said differential amplifier.
Claim 11
Dependent Claim
55 words
The combination recited in claim 7 wherein said filter means further comprises: circuit means for producing a band-rejection filter characteristic providing attenuation of said control signal in a selected band of frequencies above said second break frequency and below a third break frequency, the value of said attenuation being limited to said fixed maximum value.
Claim 12
Dependent Claim
71 words
The combination recited in claim 7 wherein said radiation responsive means comprises: a phototransistor having emitter base and collector electrodes, said emitter being connected to said inverting input terminal of said amplifier, said base corresponding to said point in said radiation responsive means and said collector for receiving a second operating potential; and wherein said first and second operating potentials are of opposite polarity taken with respect to said reference potential.
References Cited (Backward Citations)
US3770966A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-03-17 | 1978-09-16 | 1979-03-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-17 | 1982-09-16 | 1983-03-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-17 | 1986-09-16 | 1987-03-18 | $7700.00 | Window Closed / Lapsed |