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Production Test For Thermal Resistance Of Transistor

IP.com Disclosure Number: IPCOM000098205D
Original Publication Date: 1960-Apr-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Zakarias, I: AUTHOR

Abstract

The thermal resistance or K factor of a transistor is a measure of its power-handling capability. The production arrangement for determining this resistance uses the forwardly biased emitter-to-base voltage of the transistor as the temperature sensitive parameter and applies power to the collector base junction. By making the assumptions that the temperature of both junctions will be the same and that temperature dependence is really linear with a constant slope, the thermal resistance of a transistor can be derived sufficiently accurately from measurements of the applied voltages. The reasonableness of these assumptions is verifiable.

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Production Test For Thermal Resistance Of Transistor

The thermal resistance or K factor of a transistor is a measure of its power-handling capability.

The production arrangement for determining this resistance uses the forwardly biased emitter-to-base voltage of the transistor as the temperature sensitive parameter and applies power to the collector base junction. By making the assumptions that the temperature of both junctions will be the same and that temperature dependence is really linear with a constant slope, the thermal resistance of a transistor can be derived sufficiently accurately from measurements of the applied voltages. The reasonableness of these assumptions is verifiable.

The drawing represents a simplified version of a circuit arrangement for measuring the thermal resistance of a transistor 10. This arrangement has a constant current source comprising a resistor 11 and a source 12 poled forwardly to bias the emitter base junction of the transistor and establish the flow of an appropriate value of emitter current. A switch 13, when connected to its switch contact 1, connects a source 14 so as to apply a predetermined low reverse bias voltage between the collector and the base of the transistor. When the switch engages the switch contact 2, another source 15 applies a reverse bias of predetermined greater magnitude to the collector base junction of the transistor.

One terminal of a capacitor 16 is connected to the grounded terminal of source 12 while its other terminal is connected through contact 1 of a switch 17 and a resistor 18 to the emitter of the transistor. Contact 2 of switch 17 is an open contact. Switches 13 and 17 are ganged for unicontrol operation as indicated by the broken line 19.

To measure the difference between the emitter to base voltages under two distinct operating conditions (1) when the switch 13 is in engagement with its contact 1, and (2) when it is shifted to engage contact 2, a differential vacuum tube voltmeter 20 is employed. Voltmeter 20 includes a pair of triodes 21 and 22 which have their cathodes connected to ground through a resistor 23 and have their anodes connected to a source +B through resistors 24 and 25. A micro- ammeter 26, which may be calibrated in terms of thermal resistance, is connected between the anodes of the triodes.

The grid of triode 21 is connected through a resistor 27 to...