power dissipation

darkfenriz · 13th December 2004, 11:03 PM

how much power can i dissipate from a SINGLE transistor??
I mean to-3 case (probably best), huge (but not active) heatsink
cheers

Sch3mat1c · 13th December 2004, 11:25 PM

Check the datasheet.

Most TO-3's are in the 50 to 150W range.

The specification states that the case is kept at room temperature (25øC), which realistically means either very short duration use (essentially pulsed) or water cooling. A large heatsink with a few hundred watts might hold 25 above 25øC (or 40 in Australia

), or 50-65øC absolute.

If there isn't a graph of it, there's a derating spec which usually goes from say, 150W at 25 down to 0W at 175øC, so say 75W at 100øC. With good thermal contact you can assume the case is the same temp as the heatsink (plus a few degrees, you should be able to find some specs for conductivity of insulators and stuff).

Tim

AndrewT · 14th December 2004, 03:08 PM

Hi,
the highest TO3 power rating I have seen is 250w.
This is only at or below 25degrees C case temperature.
I think you could only achieve this with water cooling.
regards Andrew T.

13th December 2004, 11:03 PM	#1
darkfenriz diyAudio Member Join Date: Jun 2004 Location: Warsaw	power dissipation how much power can i dissipate from a SINGLE transistor?? I mean to-3 case (probably best), huge (but not active) heatsink cheers

13th December 2004, 11:25 PM	#2
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Check the datasheet. Most TO-3's are in the 50 to 150W range. The specification states that the case is kept at room temperature (25øC), which realistically means either very short duration use (essentially pulsed) or water cooling. A large heatsink with a few hundred watts might hold 25 above 25øC (or 40 in Australia ), or 50-65øC absolute. If there isn't a graph of it, there's a derating spec which usually goes from say, 150W at 25 down to 0W at 175øC, so say 75W at 100øC. With good thermal contact you can assume the case is the same temp as the heatsink (plus a few degrees, you should be able to find some specs for conductivity of insulators and stuff). Tim __________________ See my Electronics webpage -- the home of Vacuum Tube Drag Racing. The key to being a successful Audiophile: "I reject your reality and substitute my own!"

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14th December 2004, 03:08 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the highest TO3 power rating I have seen is 250w. This is only at or below 25degrees C case temperature. I think you could only achieve this with water cooling. regards Andrew T.

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