Patent US5821741A successfully refreshed from Google Patents.
US5821741A
Expired / Lapsed
US
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Temperature set point circuit and method employing adjustment resistor
Assignee: Analog Devices Inc
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Filing: 1997-02-07
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Granted: 1998-10-13
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Expires: 2017-02-07
Abstract
Abstract A temperature set point circuit employs a pair of bipolar transistors operated at unequal current densities, with the difference between the transistors' base-emitter voltages appearing across a trim resistor connecting their emitters. A pair of trim resistors, one of which may be external to an integrated circuit embodiment of the set point circuit, forms a resistor divider with the inter-base resistor and are selected to produce a desired temperature trip-point.
Inventors
- 👤 A. Paul Brokaw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:31
CPC Classifications
G; G05; G05F; G05F3/00; G05F3/02; G05F3/08; G05F3/10; G05F3/16; G05F3/20; G05F3/24; G05F3/242; G05F3/245; H; H03; H03K; H03K17/00; H03K17/30; Y; Y10; Y10S; Y10S323/00; Y10S323/907
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
139 words
A resistor programmable set point temperature circuit for indicating whether the temperature of a circuit meets or exceeds a set point temperature, comprising: first and second supply voltage terminals, first and second bipolar transistors of like polarity, said second transistor having an emitter area N times that of the first transistor, the emitters of both transistors coupled to a common terminal, first and second current sources connected to provide predetermined currents I1 and I2, respectively, to the collectors of said transistors, a resistor divider coupled between said first and second supply voltage terminals, a first resistor of said divider connected between the bases of said first and second transistors such that the difference in base-emitter voltages of said first and second transistors appears across said resistor, and an output stage connected to receive current from said second current source.
Claim 2
Dependent Claim
139 words
A resistor programmable set point temperature circuit for indicating whether the temperature of a circuit meets or exceeds a set point temperature, comprising: first and second supply voltage terminals, first and second bipolar transistors of like polarity, said second transistor having an emitter area N times that of the first transistor, the emitters of both transistors coupled to a common terminal, first and second current sources connected to provide predetermined currents I1 and I2, respectively, to the collectors of said transistors, a resistor divider coupled between said first and second supply voltage terminals, a first resistor of said divider connected between the bases of said first and second transistors such that the difference in base-emitter voltages of said first and second transistors appears across said resistor, and an output stage connected to receive current from said second current source.
Claim 3
Dependent Claim
107 words
The set point temperature circuit of claim 1, wherein said resistor divider further comprises: second and third resistors connected in series between the base of said second transistor and said common terminal, said second resistor having a value approximately equal to Rx-(R1q/kln(NI1/I2))(VGO-VBEO(9)/To), where R1 is the value of said first divider resistor, q is the electron charge, k is Boltzmann's constant, ln is the natural logarithm function, VGO is the bandgap voltage extrapolated to zero degrees Kelvin, Rx is a convenient resistor value chosen to produce a positive value for the resistance of the second resistor, and Tx is an offsetting temperature constant chosen to approximate (VGO/T+((m-1)k/q)ln(To/T))by(VGO/T+Tx).
Claim 4
Dependent Claim
83 words
The set point temperature circuit of claim 2, wherein said third resistor is approximately equal to (R1q/kln(NI1/I2)) (VGO/T+Tx)-Rx, where R1 is the value of said first divider resistor, q is the electron charge, k is Boltzmann's constant, ln is the natural logarithm function, VGO is the bandgap voltage extrapolated to zero degrees Kelvin, Rx is a convenient resistor value chosen to produce a positive value for the resistance of the second resistor, and Tx is an offsetting temperature constant chosen to approximate (VGO/T+((m-1)k/q)ln(To/T))by(VGO/T+Tx).
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 2001-10-12 | 2002-04-13 | 2002-10-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-10-12 | 2006-04-13 | 2006-10-13 | $3760.00 | Window Closed / Lapsed |
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