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Precision temperature sensor

a temperature sensor and precision technology, applied in the direction of thermometers, instruments, thermometers, etc., can solve the problems of adding expense and complexity to the circuit, and the typical accuracy is not enough, and achieve the effect of high precision

Inactive Publication Date: 2008-03-13
GALLI GIOVANNI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007] It is an object of the present invention to provide a highly precise temperature sensor circuit in which the voltage is linearly related to the temperature wherein trimming is not necessary.

Problems solved by technology

While conventional temperature sensing circuits provide adequate results, they are typically not precise enough unless they are subjected to trimming, for example by an external trimming circuit.
Naturally, the addition of such an external trimming circuit adds expense and complexity to the circuit.

Method used

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Embodiment Construction

[0025] As an initial matter it is useful to review some of the features of the Bi-polar Junction Transistor (BJT). FIG. 1 illustrates an example of a BJT 1. BJT's operate is substantially two regions. In the Active forward region, the collector current IC is represented by the following equation IC=Is(eVbe / Vt) and the emitter current IE=−IS (eVbe / Vt) / αF where IS is the transport saturation current of the BJT and αF is the large signal forward current gain in common base configuration. Vt is equal to KT / q where K is Boltzmann's constant, T is the absolute temperature in degrees Kelvin and q is the charge of an electron, as is noted above. At room temperature, Vt is approximately 26 mV. In the Active reverse region, IE=IS(eVbe / Vt) and IB=IS(eVbe / Vt) / βR where βR=αR / (1−αR). Thus, the emitter current may be expressed as IE=βRIB. In general IS is the transport saturation current and JS is the transport saturation current density. The other equations illustrated in FIG. 1 are based on or d...

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Abstract

A temperature sensor circuit in accordance with an embodiment of the present invention includes a temperature sensing element operable to provide a temperature voltage that is linearly related to the absolute temperature of the circuit. The temperature sensing element includes a first bi-polar junction transistor and a second bipolar junction transistor connected between a supply voltage and a common ground, wherein the base of first bipolar junction transistor is connected to the base of the second bipolar junction transistor, a first resistor connected between an emitter of the first bipolar junction transistor and the common ground and a second resistor connected between the common ground and a first node, wherein the temperature voltage is provided to the first node across the second resistor. The temperature sensor circuit also includes a current supply element operable to supply a common current to a collector of the first bipolar junction transistor, the second bipolar junction transistor and to the second resistor, respectively, an early voltage element operable to compensate for variations in voltage, a base current element operable to provide a steady base current to the bases of the first and second bipolar junction transistors, a channel modulation element operable to compensate for channel modulation and a leakage element operable to compensate for epi-substrate leakage between the circuit and a substrate on which it is formed.

Description

CROSS REFERENCE TO RELATED APPLICATION [0001] The present application claims benefit of and priority to U.S. Provisional Application No. 60 / 782,609, filed on Mar. 15, 2006, entitled PRECISION TEMPERATURE SENSOR, the entire contents of which are hereby incorporated by reference herein.BACKGROUND OF THE INVENTION [0002] The present invention relates to a precision temperature sensor circuit that provides an output voltage that is linearly related to the absolute temperature of the circuit. More specifically, the present invention relates to a precision temperature sensor circuit that eliminates the need for trimming. [0003] Monitoring the temperature of IC chips has long been a concern. Naturally, it is preferable, when possible, to incorporate the temperature sensor into the IC. It is common to use Bipolar Junction Transistors (BJT's) in temperature sensing circuits given the known temperature and current dependence of the forward-biased base-emitter junction voltage thereof. Specifi...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): G01K7/01G01K7/00
CPCG01K7/015
Inventor GALLI, GIOVANNI
Owner GALLI GIOVANNI
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