US4645948A
Expired / Lapsed
US
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Field effect transistor current source
Assignee: Nokia Bell Labs
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Filing: 1984-10-01
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Granted: 1987-02-24
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Expires: 2004-10-01
Abstract
Abstract A field effect transistor circuit generates a reference current that can obtain a desired temperature coefficient. The circuit is self-compensatory with respect to process variations, in that a "slow" process will produce a higher than normal current, while a "fast" process will give a lower one. This results in a tight spread of slew-rate, gain, gain-bandwidth, etc. in opamps, comparators, and other linear circuits. A simple adjustment in the circuit allows the temperature coefficient to be made positive or negative if so desired. An illustrative circuit is shown for CMOS technology, but can be applied to other field effect technologies.
Inventors
- 👤 Bernard L. Morris
- 👤 Jeffrey J. Nagy
- 👤 Lawrence A. Walter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 13:32
CPC Classifications
G; G05; G05F; G05F3/00; G05F3/02; G05F3/08; G05F3/10; G05F3/16; G05F3/20; G05F3/26; G05F3/262; Y; Y10; Y10S; Y10S323/00; Y10S323/907
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
135 words
An integrated circuit comprising a current source adapted to provide a controlled current to at least one device, characterized in that said current source comprises a reference field effect transistor having a gate electrode connected to a source electrode by means of a reference resistor, means for causing a reference current to flow through said reference resistor in proportion with the current that flows through the channel of said reference transistor, and means for causing said controlled current to be proportional to said reference current, wherein said current source obtains a desired variation in said reference current as a function of temperature by selecting the magnitude of at least one of: the threshold of said reference transistor (Vt); the gain of said reference transistor (β); and the channel current (I) flowing in said reference transistor.
Claim 2
Dependent Claim
135 words
An integrated circuit comprising a current source adapted to provide a controlled current to at least one device, characterized in that said current source comprises a reference field effect transistor having a gate electrode connected to a source electrode by means of a reference resistor, means for causing a reference current to flow through said reference resistor in proportion with the current that flows through the channel of said reference transistor, and means for causing said controlled current to be proportional to said reference current, wherein said current source obtains a desired variation in said reference current as a function of temperature by selecting the magnitude of at least one of: the threshold of said reference transistor (Vt); the gain of said reference transistor (β); and the channel current (I) flowing in said reference transistor.
Claim 3
Dependent Claim
78 words
The integrated circuit of claim 1 wherein said selecting is accomplished according to the formula: I.sub.R ·R=Vt+(2I/β.sub.o).sup.1/2 (T/To).sup.3/4 where: I R is the magnitude of said reference current, R is the magnitude of said reference resistor, Vt is the threshold voltage of said reference transistor, I is the channel current flowing in said reference transistor, β o is the gain of said reference transistor at a reference temperature To, and T is the temperature of said reference transistor.
Claim 4
Dependent Claim
37 words
The integrated circuit of claim 1 wherein said integrated circuit comprises at least one field effect transistor of a first channel conductivity type, and at least one transistor having a channel conductivity type opposite said first type.
Claim 5
Dependent Claim
78 words
The integrated circuit of claim 1 wherein said integrated circuit is formed in a semiconductor substrate comprising at least one first region of said first conductivity type having a plurality of field effect transistors formed therein, and further comprising a second region of said second conductivity type wherein said control field effect transistor is formed, with said second region being isolated by a p-n junction from the region wherein the other of said field effect transistors are formed.
Claim 6
Dependent Claim
22 words
The integrated circuit of claim 4 wherein the source of said control field effect transistor is electrically connected to said isolation region.
Claim 7
Dependent Claim
16 words
The integrated circuit of claim 1 wherein said field effect transistors are metal-oxide-silicon field effect transistors.
Claim 8
Dependent Claim
20 words
The integrated circuit of claim 1 wherein said reference field transistor has its back-gate electrode connected to a reference voltage.
Claim 9
Dependent Claim
22 words
The integrated circuit of claim 1 wherein said reference resistor has a resistance in the range of 100 ohms to 10 megaohms.
Claim 10
Dependent Claim
34 words
The integrated circuit of claim 1 wherein said reference resistor has a size defined at least in part by a layer of material that also comprises the gate electrode of said field effect transistor.
Claim 11
Dependent Claim
11 words
The integrated circuit of claim 9 wherein said material comprises polysilicon.
Claim 12
Dependent Claim
13 words
The integrated circuit of claim 9 wherein said material comprises a metal silicide.
Claim 13
Dependent Claim
34 words
The integrated circuit of claim 1 wherein said at least one device that is provided with said controlled current is a solid state device formed on the same semiconductor substrate as said current source.
Claim 14
Dependent Claim
18 words
The integrated circuit of claim 12 wherein an operational amplifier comprises said device that receives a controlled current.
Claim 15
Dependent Claim
17 words
The integrated circuit of claim 12 wherein a comparator comprises said device that receives a controlled current.
Claim 16
Dependent Claim
25 words
The integrated circuit of claim 12 wherein said at least one device that receives a controlled current is included in at least one logic circuit.
Claim 17
Dependent Claim
26 words
The integrated of claim 12 wherein said at least one device that receives a controlled current produces therefrom a controlled voltage having a desired temperature coefficient.
Claim 18
Dependent Claim
19 words
The integrated circuit of claim 1, wherein said integrated circuit is formed on a separate substrate from said device.
Claim 19
Dependent Claim
21 words
The integrated circuit of claim 1 wherein said integrated circuit is adapted to provide said controlled current to an optical emitter.
Claim 20
Dependent Claim
22 words
The integrated circuit of claim 1 wherein said controlled current has a positive temperature coefficient over a desired range of operating temperatures.
Claim 21
Dependent Claim
22 words
The integrated circuit of claim 1 wherein said controlled current has a negative temperature coefficient over a desired range of operating temperatures.
Claim 22
Dependent Claim
23 words
The integrated circuit of claim 1 wherein said controlled current has an approximately zero temperature coefficient over a desired range of operating temperatures.
Claim 23
Dependent Claim
32 words
The integrated circuit of claim 1 wherein said controlled current varies less than plus or minus five percent of its average value over a temperature range of from 0° to 100° C.
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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) | 1990-02-23 | 1990-08-25 | 1991-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-23 | 1994-08-25 | 1995-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-23 | 1998-08-25 | 1999-02-24 | $7700.00 | Window Closed / Lapsed |