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# Transistor Thermal Resistance Test

IP.com Disclosure Number: IPCOM000096944D
Original Publication Date: 1962-Feb-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 32K

IBM

## Related People

Squarzini, J: AUTHOR

## Abstract

The thermal resistance of a transistor is a measure of its power handling capability. The forwardly biased emitter-to-base voltage of a test transistor is used as the temperature sensitive parameter. Then, the thermal resistance of the device is ascertained by measuring the change in base-emitter voltage with respect to the change in collector voltage and emitter current. When these parameters are determined, they are applied in a formula to determine the thermal resistance value. The formula is as follows: RT=(delta Veb - Kl delta Vc - K3 delta Ie)K2/delta P where Veb is the base-emitter voltage, Vc is the collector voltage, Ie is the emitter current, and P is the power of the device.

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Transistor Thermal Resistance Test

The thermal resistance of a transistor is a measure of its power handling capability. The forwardly biased emitter-to-base voltage of a test transistor is used as the temperature sensitive parameter. Then, the thermal resistance of the device is ascertained by measuring the change in base-emitter voltage with respect to the change in collector voltage and emitter current. When these parameters are determined, they are applied in a formula to determine the thermal resistance value. The formula is as follows: RT=(delta Veb - Kl delta Vc - K3 delta Ie)K2/delta P where Veb is the base-emitter voltage, Vc is the collector voltage, Ie is the emitter current, and P is the power of the device.

The constants K1, K2 and K3 have fixed values for a given type of transistor. Therefore, once they are determined for a particular transistor type, any number of transistors of that type can be tested by determining the change in parameters. The values of the constants are:
K1 = delta Veb(1) - K3 delta Ie(1)/Vc(1)

K2 = delta Veb/ delta T at Vc = constant, Ie = constant K3 = delta Veb(2) + K2 delta T(2)/ deltaIe(2) where (1) and (2) indicate two levels of test which are not necessarily the same, and T is the temperature of the forwardly biased junction. With this arrangement, the emitter current parameter is kept constant, and, therefore, this term of the formula drops out.

The transistor T to be tested is connected in grounded base configuration....