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Transistor Thermal Resistance Measurements

IP.com Disclosure Number: IPCOM000074520D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Liang, RN: AUTHOR

Abstract

Two collector currents of three or more decades apart are applied to a transistor in measuring its thermal resistance. The corresponding base-to-emitter voltage drops of the transistor are then sequentially measured at a specific junction temperature. A constant relation with temperature is obtained from the differential of these voltage drops.

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Transistor Thermal Resistance Measurements

Two collector currents of three or more decades apart are applied to a transistor in measuring its thermal resistance. The corresponding base-to- emitter voltage drops of the transistor are then sequentially measured at a specific junction temperature. A constant relation with temperature is obtained from the differential of these voltage drops.

Operational amplifiers 1-5 are used in the test circuit. One power pulse is used to measure both voltage drops. Before the transistor under test (TUT) is heated up, the measuring circuit stores the initial base-to-emitter voltage drop in amplifier 2 through switch SW3 with the collector current input switching from ic1 to ic2. Thereafter, switches SW1 and SW2 are switched to a heating circuit 6 for a duration of one second and then switched back to the measuring circuit. Collector currents ic1 and ic2 are applied within 30 microseconds of each other. The resulting base-to-emitter voltage drop for the two currents is measured and their differential is stored in amplifier 3.

Amplifier 4 provides the difference between the initial unheated base-to- emitter voltage drop and the heated base-to-emitter voltage drop. This difference voltage is supplied to amplifier 5 which acts as a scaler to adjust for the temperature coefficient and the power input to TUT. It acts as a digital divider providing a direct digital indication of the thermal resistance of TUT.

The thermal resistance of the...