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Temperature Transducer and Thermally Coupled Switch

IP.com Disclosure Number: IPCOM000091047D
Original Publication Date: 1969-Sep-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 29K

Publishing Venue

IBM

Related People

Schlig, ES: AUTHOR

Abstract

A differential circuit which functions as a localized temperature sensing circuit is shown in drawing 1. This is a basic differential amplifier in which there is no applied electrical differential input. The bases of Q1 and Q2 are tied together, as are the emitters of these transistors. The input to the circuit is the difference in temperature of Q1 and Q2 and the output is the collector current changes of these transistors due to the temperature changes.

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Temperature Transducer and Thermally Coupled Switch

A differential circuit which functions as a localized temperature sensing circuit is shown in drawing 1. This is a basic differential amplifier in which there is no applied electrical differential input. The bases of Q1 and Q2 are tied together, as are the emitters of these transistors. The input to the circuit is the difference in temperature of Q1 and Q2 and the output is the collector current changes of these transistors due to the temperature changes.

In the quiescent state, current I divides between the emitters of Q1 and Q2, resulting in collector current flow. Changes in temperature difference between the emitter junctions of Q1 and Q2 result in changes in the division of current 1 between Q1 and Q2. This causes different collector currents to flow in Q1 and Q2. The total current remains approximately constant. The circuit is insensitive to common mode temperature changes.

The drawing 2 circuit provides for electric inputs. These electrical inputs are voltage changes applied to either the collector of Q1 at A or to both collectors differentially at A and B. The electrical outputs are the resultant current or voltage changes at the collectors of either Q1 or Q2 or both. Electrical input voltage changes result in power dissipation changes. The temperature of the transistor to which the input is applied changes slowly in response to the power dissipation change, causing changes in the collector currents as in the circuit of drawing 1. Although Q1 and Q2 are typically integrated into a semiconductor chip, temperature changes occur independently in Q1 and Q2 because of the localized nature of the thermal spreading resistance of the active region of transistors.

The circuit is insensitive to common mode temperature changes due to more remote thermal resistances common to Q1 and Q2.

Because of the slow response of temperature to changes in power dissipation, fast rising steps in...