Browse Prior Art Database

Temperature Sensor

IP.com Disclosure Number: IPCOM000052021D
Original Publication Date: 1981-Apr-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Paradise, ED: AUTHOR

Abstract

An integrated-circuit temperature sensor can be formed on a single chip so as to provide an output voltage V(T) that is sensitive to the temperature of the chip. The circuit includes a plurality of transistors or devices connected as shown in the figure and as described below.

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Temperature Sensor

An integrated-circuit temperature sensor can be formed on a single chip so as to provide an output voltage V(T) that is sensitive to the temperature of the chip. The circuit includes a plurality of transistors or devices connected as shown in the figure and as described below.

In the sensor, it can be shown that the change in Voltage V(T) with respect to a change in temperature T of the chip is: d(V(T)) over d(T) = 4nK over q 1n I(A) over I(B) (1) where n = normality constant
K = Boltzman's constant q = charge on electron
I(A) = current flowing through serially connected devices TC - TF

I(B) = current flowing through serially connected groups GB - GE of n parallel connected devices.

A current I flows through resistor R and device TA. Such current is then reflected by the parallel connected m devices of group GA to produce a current mI or I(A). Such current is also reflected in groups GB - GE by transistor TB and is split into n equal divisions by the parallel devices.

The ratio of I(A)/I(B) = mn, and this is a constant for a given number of devices. Thus, relative to Equation 1, by keeping the ratio I(A)/I(B) constant, the change in the output voltage V(T) with respect to temperature is process independent.

In an exemplary sensor, m = 63 and n = 16 so that the total number of devices in the sensor is 133. Such a sensor has an accuracy of +/- 2 degrees C.

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