[TenTec] Followup - Jupiter Overheating

Dr. Gerald N. Johnson, electrical engineer geraldj@isunet.net
Wed, 17 Apr 2002 10:24:11 -0500

Leaky transistor... A bipolar transistor is operated with one junction
reversed biased (base to collector). If that junction is leaky, not
super high resistance, the collector voltage will leak some current
through the leakage and add to the base bias and cause the transistor to
draw collector current (of current gain times the leakage current) even
when not being driven. Leakage tends to be very temperature sensitive
rising rapidly with junction or package temperature, so its often a run
away condition where a little leakage heats the transistor leading to
more leakage and the spiral can be rapid to transistor melting in the
worst cases. Silicon transistors tend to not have a leakage problem
unless faulty. Germanium transistors tended to not be free from such
leakage and circuits had to accept the leakage to have any reliability
at all.

73, Jerry, K0CQ
Entire content copyright Dr. Gerald N. Johnson. Reproduction by
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