From: Tom MacIntyre
Subject: Re: Thermal runaway: please settle this dispute!
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Date: Sat, 04 Jan 2003 19:51:36 GMT
NNTP-Posting-Date: Sat, 04 Jan 2003 15:51:36 AST
On Thu, 02 Jan 2003 12:47:47 +0000, Paul Burridge
>I ended up having a bit of a disagreement with a friend of mine over
>the holiday concerning thermal runaway in a BJT.
>I maintain that an increase in temperature across the emitter diode
>leads to a fall in that junction's barrier height, making the
>so-called 'energy hill' easier to overcome for the forward biased
>current flowing through it. The causes increased current flow, giving
>rise to further heating of the emitter diode, thereby lowering the
>barrier potential still further and so on until the device is
>destroyed. The fall in barrier height is around 2mV per degree C., if
>I recall correctly.
>My friend, OTOH, maintains that it's nothing to do with the
>emitter/base junction at all, but solely arises due to an increase in
>temperature at the collector, causing the same cycle of
>heating/increased current until the device is destroyed.
>So what is the panel's view on the subject? I always believed I was
>right, but this chap is regarded as pretty eminent in electronics so I
>can't simply dismiss his views out of hand.
Are they mutually exclusive?