| Electronics > Projects, Designs, and Technical Stuff |
| High current transistor connections |
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| T3sl4co1l:
Yeah, this screams other design issues. An SMPS with extra filtering is a strong contender here as well, even if you have a very tight noise requirement. Tim |
| MagicSmoker:
--- Quote from: David Hess on February 15, 2019, 03:00:52 pm ---... I would not use a socket at such high currents. ... --- End quote --- Normally I would advise the same, but not in this case... because the transistor is guaranteed to fail and a socket will make cooking its replacement easier. |
| IconicPCB:
Thank You for Your opinions. Allvalidaddressing the issues of TO-3 packaging. A yes to all of the above comments. I have seen some devices packaged in srew downterminal power packages. ON semi has only one such part number. Central semiconductor do not list anything. Any other part numbers recomendations are welcome.. |
| David Hess:
--- Quote from: MagicSmoker on February 15, 2019, 05:43:12 pm --- --- Quote from: David Hess on February 15, 2019, 03:00:52 pm ---... I would not use a socket at such high currents. ... --- End quote --- Normally I would advise the same, but not in this case... because the transistor is guaranteed to fail and a socket will make cooking its replacement easier. --- End quote --- There are some big collet sockets made for 60 mil pins that might handle 50 amps. I have seen them used on older Intel VRM designs among other things. I cannot say that I have seen them used with power transistors but it would not be apparent unless they were removed. I would not rely on the standard TO-3 transistor socket which relies on two points of contact with each pin. |
| Doctorandus_P:
--- Quote from: David Hess on February 15, 2019, 03:47:35 pm ---When using high-power amplifiers, there are certain problems you just never have if you use a big-enough heat sink. This heat sink's thermal resistance is lower than 0.5 C/W. - Figure 7.4, page 84, Troubleshooting Analog Circuits, Robert Pease The photograph shows a TO-3 style part mounted to a cylinder head from VW engine. --- End quote --- Ok, and 0.5C/Watt will will give a 150C temperature rise of the aluminimum @ 300W dissipation. And we're not even talking about junction temperature here, nor about what's left on SOA for the transistor at such temperatures. More glass and thinner pins also do not help with more current. It somehow reminds me of MOSfets which can handle redicilous currents, even in TO220. One of the datasheets I saw stated a current of 350A for the chip, but with an asterisk and a note that the pins start to melt at 150A or so. |
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