Pressure transducer using integrated circuit elements

• US 4,558,238 A
• Filed: 09/29/1983
• Issued: 12/10/1985
• Est. Priority Date: 10/01/1982
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kato, Kazuo, Sato, Hideo, Yamada, Kazuji, Kawakami, Kanji, Sasayama, Takao, Kitadate, Yukitaka
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): HUDSPETH, DAVID R
• Application Number:
  US06/536,870
• Time in Patent Office: 803 Days
• Field of Search: 73/708, 73/720, 73/721, 73/726, 73/727, 307/491-493, 307/297, 307/308, 307/310, 323/312-314, 323/907, 338/3, 338/4
• US Class Current: 327/540
• CPC Class Codes: G01L 9/065 with temperature compensating means non electric temperature compensating means G01L19/04
• CPC Class Codes: Y10S 323/907 Temperature compensation of semiconductor

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.

Claims

1. 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.

2. 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.

3. A pressure transducer according to claim 2 further including a third transistor for compensating current amplification factors of said two transistors.

4. 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.

5. 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.

6. 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.