Bill is entirely correct.
Once in my prior career, I did a study of Mean Time Between Failure for
IC circuits (same applies to transistors). That study had to consider
the case temperature of the IC (or transistor) with respect to the
junction temperature.
The specification for the IC or transistor package will include a
thermal resistance parameter, which must be considered to obtain the
maximum temperature for the case of the device.
Bill's comment about the screw tightness is entirely correct - the heat
of the device case must be transferred to the heatsink in an efficient
manner.
73,
Don W3FPR
On 10/27/2017 6:07 PM, Nr4c wrote:
Yes. But I believe that is Junction temperature, not case on heatsink temp.
Remember the case bottom is heatsink for those. Make sure screws are tight.
Sent from my iPhone
...nr4c. bill
On Oct 27, 2017, at 12:19 PM, N2TK, Tony <[email protected]> wrote:
50C is not hot for a transistor. Commercial transistors are usually speced to
85C. JANS (space) transistors are speced to 125C and actually baked without
bias for 320 hours at 200C. The hFE is measured before and after to check for
change.
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