US5546041A
Expired / Lapsed
US
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Feedback sensor circuit
Assignee: Massachusetts Institute of Technology
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Filing: 1993-08-05
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Granted: 1996-08-13
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Expires: 2013-08-05
Abstract
Abstract A circuit for sensing a parameter, such as temperature, has a single current source and a mismatched differential pair for providing two different currents at a desired current ratio. Each current is provided to a current control element and a sensing element, each of which may be diodes. An operational amplifier closes the loop and feeds back a signal from the input of the current control elements to the differential pair to hold the desired current ratio constant. Chopper circuitry is employed with the amplifier to reduce the offset and low frequency noise contribution of the amplifier.
Inventors
- 👤 Kenneth S. Szajda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 01:35
CPC Classifications
H; H03; H03F; H03F3/00; H03F3/04; H03F3/08; H03F3/082; G; G01; G01K; G01K7/00; G01K7/01
Claims Analysis
Total Claims: 40
Claim 1
Independent Claim
93 words
A circuit comprising: two sensor; an excitation source having a separate excitation control element for providing an excitation signal to each sensor, said excitation signals being at a fixed ratio for at least one of their characteristics; a control circuit coupled to the sensors for maintaining the excitation signals at the fixed ratio regardless of temperature changes, said control circuit including a feedback network for providing a separate feedback signal to each of said excitation control elements; and output terminals for obtaining a signal from said sensors indicative of a selected sensed parameter.
Claim 2
Dependent Claim
93 words
A circuit comprising: two sensor; an excitation source having a separate excitation control element for providing an excitation signal to each sensor, said excitation signals being at a fixed ratio for at least one of their characteristics; a control circuit coupled to the sensors for maintaining the excitation signals at the fixed ratio regardless of temperature changes, said control circuit including a feedback network for providing a separate feedback signal to each of said excitation control elements; and output terminals for obtaining a signal from said sensors indicative of a selected sensed parameter.
Claim 3
Dependent Claim
68 words
The circuit of claim 1 wherein the control circuit further comprises: two current control elements, each of which has an input terminal, and each of which is coupled to a respective sensor of said two sensors; and a feedback network coupled to the input terminal of each current control element, for feeding back a signal to the excitation source to maintain the excitation signals at the fixed ratio.
Claim 4
Dependent Claim
34 words
The circuit of claim 2 wherein the two sensors each has an input terminal coupled to a respective output of the current control elements, and an output terminal of said each sensor is grounded.
Claim 5
Dependent Claim
33 words
The circuit of claim 2 wherein the two sensors each has an output terminal coupled to the respective input of the current control elements, the outputs of the current control elements being grounded.
Claim 6
Dependent Claim
13 words
The circuit of claim 2 wherein the feedback network comprises an operational amplifier.
Claim 7
Dependent Claim
25 words
The circuit of claim 5 wherein the feedback network further comprises chopper circuitry for modulating the input to the amplifier, and for demodulating the output.
Claim 8
Dependent Claim
30 words
The circuit of claim 6 wherein the excitation source is a current source and the excitation control elements include a differential transistor pair for providing currents at the fixed ration.
Claim 9
Dependent Claim
24 words
The circuit of claim 7 wherein outputs of the operational amplifier are respectively coupled to control inputs of the transistors in the differential pair.
Claim 10
Dependent Claim
10 words
The circuit of claim 8 wherein the sensors comprise diodes.
Claim 11
Dependent Claim
12 words
The circuit of claim 9 wherein the current control elements comprise diodes.
Claim 12
Dependent Claim
21 words
The circuit of claim 10 wherein the sensors are matched diodes, and the control elements pass current at the fixed ratio.
Claim 13
Dependent Claim
13 words
The circuit of claim 10 wherein the sensors are used to measure temperature.
Claim 14
Dependent Claim
24 words
The circuit of claim 1 wherein the two sensors each have input terminals coupled to the control circuit, and output terminals which are grounded.
Claim 15
Dependent Claim
46 words
The circuit of claim 1 wherein the control circuit comprises two current control elements, each coupled in series with respective sensor of said two sensors, and wherein the two sensors each have output terminals coupled to the current control elements, the current control elements being grounded.
Claim 16
Dependent Claim
32 words
The circuit of claim 1 wherein the excitation source comprises a current source and a differential transistor pair which provides currents to each sensor of said two sensors at the fixed ratio.
Claim 17
Dependent Claim
66 words
The circuit of claim 15 wherein the control circuit further comprises: two current control elements, each of which has an input terminal, and each of which is coupled to a respective sensor of said two sensors; and the feedback network is coupled to the input terminal of each current control element, for feeding back a signal to both of the transistors in the differential transistor pair.
Claim 18
Dependent Claim
12 words
The circuit of claim 16 wherein the current control elements comprise diodes.
Claim 19
Dependent Claim
16 words
The circuit of claim 1 wherein the sensors are integrated silicon sensors fabricated on a chip.
Claim 20
Dependent Claim
10 words
The circuit of claim 1 wherein the sensors sense temperature.
Claim 21
Dependent Claim
10 words
The circuit of claim 1 wherein the sensors sense light.
Claim 22
Dependent Claim
10 words
The circuit of claim 1 wherein the sensors sense radiation.
Claim 23
Dependent Claim
14 words
The circuit of claim 1 wherein the circuit is fabricated on a single chip.
Claim 24
Dependent Claim
126 words
A circuit comprising: a first sensor; a first current control element coupled to the first sensor; a second sensor; a second current control element coupled to the second sensor; current source circuitry for providing a first current and a second current having a selected ratio to the first and second sensors and to the first and second current control elements along first and second current paths; feedback circuitry for receiving inputs from the first and second current paths and for providing separate outputs to the current source circuitry for the first and second currents respectively to maintain the first and second currents at the fixed ratio regardless of temperature changes; and output terminals for obtaining a signal from said sensors indicative of a selected sensed parameter.
Claim 25
Dependent Claim
126 words
A circuit comprising: a first sensor; a first current control element coupled to the first sensor; a second sensor; a second current control element coupled to the second sensor; current source circuitry for providing a first current and a second current having a selected ratio to the first and second sensors and to the first and second current control elements along first and second current paths; feedback circuitry for receiving inputs from the first and second current paths and for providing separate outputs to the current source circuitry for the first and second currents respectively to maintain the first and second currents at the fixed ratio regardless of temperature changes; and output terminals for obtaining a signal from said sensors indicative of a selected sensed parameter.
Claim 26
Dependent Claim
11 words
The circuit of claim 23 wherein each sensor comprises a diode.
Claim 27
Dependent Claim
28 words
The circuit of claim 24 wherein the current source circuitry comprises: a current source; and a mismatched differential transistor pair coupled to the output of the current source.
Claim 28
Dependent Claim
31 words
The circuit of claim 23 wherein the feedback circuitry comprises an operational amplifier and chopper circuitry for modulating the input to the amplifier and for demodulating the output from the amplifier.
Claim 29
Dependent Claim
13 words
The circuit of claim 23 wherein the sensor elements are sensitive to temperature.
Claim 30
Dependent Claim
13 words
The circuit of claim 23 wherein the sensor elements are sensitive to light.
Claim 31
Dependent Claim
13 words
The circuit of claim 23 wherein the sensor elements are sensitive to radiation.
Claim 32
Dependent Claim
43 words
The circuit of claim 23 wherein the first current control element and the first sensor are in series, and the second current control element and second sensor are in series, wherein the feedback circuit is coupled to inputs of the current control elements.
Claim 33
Dependent Claim
28 words
The circuit of claim 30 wherein the current source circuitry comprises: a current source; and a mismatched differential transistor pair coupled to the output of the current source.
Claim 34
Dependent Claim
23 words
The circuit of claim 31 wherein the feedback circuit is an operational amplifier which has an output coupled to the differential transistor pair.
Claim 35
Dependent Claim
9 words
The circuit of claim 32 wherein sensors are diodes.
Claim 36
Dependent Claim
85 words
The circuit of claim 23 wherein each sensor element is a diode; each current control element is a diode; the current source circuitry comprises a current source and a mismatched transistor pair for providing two currents at a fixed ratio, and the feedback circuitry comprises: an operational amplifier for receiving voltage inputs at the inputs to the current control diodes and for providing outputs to the transistor pair; and chopper circuitry for modulating and demodulating the inputs and output to and from the operational amplifier.
Claim 37
Dependent Claim
105 words
A circuit comprising: first means for sensing a parameter; second means for sensing a parameter; means for providing a first current and a second current to each of the first and second means for sensing, respectively, the first and second currents having a fixed ratio; means for controlling the first and second currents to maintain the fixed ratio regardless of temperature changes, said means for controlling including a feedback network for providing a separate feedback signal to the means for providing for said first current and for said second current; and output terminals for obtaining a signal from said sensors indicative of the sensed parameter.
Claim 38
Dependent Claim
105 words
A circuit comprising: first means for sensing a parameter; second means for sensing a parameter; means for providing a first current and a second current to each of the first and second means for sensing, respectively, the first and second currents having a fixed ratio; means for controlling the first and second currents to maintain the fixed ratio regardless of temperature changes, said means for controlling including a feedback network for providing a separate feedback signal to the means for providing for said first current and for said second current; and output terminals for obtaining a signal from said sensors indicative of the sensed parameter.
Claim 39
Dependent Claim
35 words
The circuit of claim 35 wherein the means for providing a first current and a second current comprises: means for providing a source current; and means for dividing the source current in the fixed ratio.
Claim 40
Dependent Claim
19 words
The circuit of claim 36 wherein the feedback network feeds back a feedback signal to the means for dividing.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-08-13 | 2000-02-12 | 2000-08-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-08-13 | 2004-02-12 | 2004-08-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-08-13 | 2008-02-12 | 2008-08-13 | $7700.00 | Window Closed / Lapsed |