| 摘要 |
890,841. Semi-conductor devices. STANDARD TELEPHONES & CABLES Ltd. Sept. 26, 1958 [Sept. 27, 1957], No. 30826/58. Class 37. A power transistor is mounted on an electrically and heat conductive support with a region of heat conductive semi-conductor of opposite conductivity type to the adjacent zone of the transistor disposed between said zone and the support. The PN junction formed between the region and the adjacent zone of the transistor is reverse biased in operation to prevent leakage of current to earth. In one embodiment, Fig. 1, a conventional junction transistor of the type in which the collector zone is in direct contact with the casing 9 to facilitate cooling is mounted on an earthed metal chassis through the intermediary of a semi-conductor washer 15 of opposite conductivity type to the collector zone. Alternatively, a washer with a PN junction between its opposite faces may be used. The mounting nut and washer 13, 18 are insulated from the chassis by grommet 17. In another embodiment, Fig. 3, a junction transistor is mounted in a casing 27 on the head of mounting bolt 24. In this case the collector zone is isolated from the casing and bolt by a semi-conductor coating or body 25, of opposite conductivity type to that of the collector zone, on the head of the mounting bolt. The casing may in this case be mounted as shown direct to the chassis. In each of these embodiments the collector zone may be maintained positive or negative to earth respectively when it is N or P type while being in good thermal contact through the additional semi-conductor body with the chassis. |
