US4558238A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Pressure transducer using integrated circuit elements
Assignee: Hitachi Ltd
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Filing: 1983-09-29
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Granted: 1985-12-10
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Expires: 2003-09-29
Abstract
Abstract A pressure transducer comprises a pressure sensor including a bridge connection of gauging resistors formed on a semiconductor substrate, and a power supply connected to the pressure sensor for driving it and basically acting as a constant current source. The power supply includes at least two transistors formed on the semiconductor substrate. One of the transistors provides a collector current which is less in temperature-dependency relative to that of the other transistor, and the other transistor has a collector circuit connected to the pressure sensor and provides a collector current corresponding to a sum of a substantially temperature-dependent current and a substantially temperature-independent current. A ratio of the temperature-dependent current to the temperature-independent current is adjusted by selecting operation characteristics of the two transistors such that a temperature characteristic of the collector current of the other transistor is substantially inversely proportional to a temperature characteristic of the output of the pressure sensor when it is driven with a constant voltage.
Inventors
- 👤 Kazuji Yamada
- 👤 Hideo Sato
- 👤 Yukitaka Kitadate
- 👤 Kanji Kawakami
- 👤 Kazuo Kato
- 👤 Takao Sasayama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 13:17
CPC Classifications
G; G01; G01L; G01L9/00; G01L9/02; G01L9/06; G01L9/065; Y; Y10; Y10S; Y10S323/00; Y10S323/907
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
167 words
A pressure transducer comprising: a semiconductor substrate; a pressure sensor including a bridge connection of gauging resistors formed on said semiconductor substrate; and a power supply connected to said pressure sensor for driving said pressure sensor, said power supply basically acting as a condtant current source and including at least two transistors formed on said semiconductor substrate, wherein one of said transistors provides a collector current which is less in temperature dependency relative to that of the other transistor and, the other transistor has a collector circuit connected to said pressure sensor and providing a collector current corresponding to a sum of a substantially temperature-dependent current and a substantially temperature-independent current, and a ratio of said temperature-dependent current to said temperature-independent current is adjusted by selecting operation characteristics of said two transistors such that a temperature characteristic of the collector current of said other transistor is substantially inversely proportional to a temperature characteristic of said pressure sensor when said pressure sensor is driven with a constant voltage.
Claim 2
Dependent Claim
167 words
A pressure transducer comprising: a semiconductor substrate; a pressure sensor including a bridge connection of gauging resistors formed on said semiconductor substrate; and a power supply connected to said pressure sensor for driving said pressure sensor, said power supply basically acting as a condtant current source and including at least two transistors formed on said semiconductor substrate, wherein one of said transistors provides a collector current which is less in temperature dependency relative to that of the other transistor and, the other transistor has a collector circuit connected to said pressure sensor and providing a collector current corresponding to a sum of a substantially temperature-dependent current and a substantially temperature-independent current, and a ratio of said temperature-dependent current to said temperature-independent current is adjusted by selecting operation characteristics of said two transistors such that a temperature characteristic of the collector current of said other transistor is substantially inversely proportional to a temperature characteristic of said pressure sensor when said pressure sensor is driven with a constant voltage.
Claim 3
Dependent Claim
28 words
A pressure transducer according to claim 1 wherein the operation characteristics of said two transistors are adjusted by varying a ratio of emitter areas of said two transistors.
Claim 4
Dependent Claim
21 words
A pressure transducer according to claim 2 further including a third transistor for compensating current amplification factors of said two transistors.
Claim 5
Dependent Claim
40 words
A pressure transducer according to claim 2 wherein said two transistors are pnp transistors, an essentially temperature-independent resistor is connected to the collector circuit of said other transistor, and a voltage across said resistor is applied to said pressure sensor.
Claim 6
Dependent Claim
46 words
A pressure transducer according to claim 2 wherein said two transistors are npn transistors, and the collector circuit of said other transistor is applied through a current miller circuit to a substantially temperature-independent resistor and a voltage across said resistor is applied to said pressure sensor.
Claim 7
Dependent Claim
37 words
A pressure transducer according to claim 1 wherein an output of said pressure sensor is supplied to an amplifier having a temperature-dependent gain and said pressure sensor is driven by the collector current of said other transistor.
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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) | 1988-12-09 | 1989-06-10 | 1989-12-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-09 | 1993-06-10 | 1993-12-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-09 | 1997-06-10 | 1997-12-10 | $7700.00 | Window Closed / Lapsed |