Hi!
I'm new in this forum, most of the time I just read and find it's very informative but now I need to ask a question.
I would just like to ask your comments on which is better or easier to keep cool, transistors in TO-3 package or the plastic ones (TO-247) for output of power amps.
Tnx!
Jojo
I'm new in this forum, most of the time I just read and find it's very informative but now I need to ask a question.
I would just like to ask your comments on which is better or easier to keep cool, transistors in TO-3 package or the plastic ones (TO-247) for output of power amps.
Tnx!
Jojo
Rare because they are more expensive than plastic and more difficult to mount. TO 3 is a very good case for heavy applications considering it's thermal characteristics.
Same story as why DIL/DIP disappears: production costs. Although I missed the explanation of producers like they give with SMD components:
- "the market demands it"
- "it has lower lead inductance"
- "better RF characteristics"
- "it is to big"
Same story as why DIL/DIP disappears: production costs. Although I missed the explanation of producers like they give with SMD components:
- "the market demands it"
- "it has lower lead inductance"
- "better RF characteristics"
- "it is to big"
Indeed Jean-Paul.
Another thing to note is that the package is only part of the story. Thermal resistance is much like electrical resistance. From the transistor chip to ambient air you first have to go from chip to package which has a certain resistance in deg Celcius/Watt, then to the washer, then to the heatsink, then to ambient. Each junction adds a thermal resistor in series. At the and you arrive at say .75deg/W for the TO3 and .80 for the plastic, not a great deal and easily compensated for by increasing the heatsink a little if it were critical. And it is only for interest in class A applications anyway.
Modern, wideband power transistors for audio are as far as I know all packaged in plastic.
Jan Didden
Another thing to note is that the package is only part of the story. Thermal resistance is much like electrical resistance. From the transistor chip to ambient air you first have to go from chip to package which has a certain resistance in deg Celcius/Watt, then to the washer, then to the heatsink, then to ambient. Each junction adds a thermal resistor in series. At the and you arrive at say .75deg/W for the TO3 and .80 for the plastic, not a great deal and easily compensated for by increasing the heatsink a little if it were critical. And it is only for interest in class A applications anyway.
Modern, wideband power transistors for audio are as far as I know all packaged in plastic.
Jan Didden
Morph said:
Well, as far as I know, the MJ's are not really as wideband as the plastic Toshiba's and othe MJE's. They are really old horses. And the one with the 8 pins probably is a regulator or something, and I would bet that is also old and not used in new designs anymore.
Jan Didden
Edit: just did a quick check on the MJ15003: Hfe=25 @ 5A, Ft=2Mhz. These are really only fit for heating or controlling car window movers. For audio these are only worth a good laugh!
Not sure if you are referring to me, Morph. 
But you are right about newer components in a TO 3 case as I checked. So it seems some newer real power components are still made in TO 3. Must have something to do with thermal characteristics,don't you think ?
For me TO 3 and DIL/DIP are more or less examples of easy-to-work-with devices ( yes, TO 3 too ! ) and seeing them disappear from the market doesn't make me happy.
But you are right about newer components in a TO 3 case as I checked. So it seems some newer real power components are still made in TO 3. Must have something to do with thermal characteristics,don't you think ?
For me TO 3 and DIL/DIP are more or less examples of easy-to-work-with devices ( yes, TO 3 too ! ) and seeing them disappear from the market doesn't make me happy.
No jean-paul i wasn't refering to you.
And I too am sorry to see the disapearence of DIY friendly semi-conductor packages.
unfortuantly some people seem to think anything over 5 years old is only fit for powering car windows, tell that to the valve lovers.
You can still get valves that were designed more than 50 years ago, so there is hope.
And I too am sorry to see the disapearence of DIY friendly semi-conductor packages.
unfortuantly some people seem to think anything over 5 years old is only fit for powering car windows, tell that to the valve lovers.
You can still get valves that were designed more than 50 years ago, so there is hope.
Boy, what mood are we in today?Morph said:
I think we all can agree that no, I mean no electronic designer today would choose TO-3 if he not had to. TO-3 is history. How many of you have seen NEW devices in TO-3? Not very common. My balance point of view is that TO-3 is "yesterday". The market has said so.
TO3 stuff
Probably he was referring to me..
I did take the trouble to check the data sheet for the MJ's and gave straight numbers. He should be able to cope with that.
As far as the 8-pin BB is concerned, I didn't have the facts, I just said "I bet...". I didn't feel like checking the whole BB catalog as he neglected to mention a type number. If he would do it, I would check, because I am willing to learn.
Opinionated? Yes, aren't we all?
There is one thing I take exception to. Anyone who knows me from my posts knows that I am the first to present a balanced viewpoint. His judgement is troubled by his frustration.
Jan Didden
Probably he was referring to me..
I did take the trouble to check the data sheet for the MJ's and gave straight numbers. He should be able to cope with that.
As far as the 8-pin BB is concerned, I didn't have the facts, I just said "I bet...". I didn't feel like checking the whole BB catalog as he neglected to mention a type number. If he would do it, I would check, because I am willing to learn.
Opinionated? Yes, aren't we all?
There is one thing I take exception to. Anyone who knows me from my posts knows that I am the first to present a balanced viewpoint. His judgement is troubled by his frustration.
Jan Didden
I have some that will handle a dissipation of 540 watts. Small Print -> (provided ypu keep the tab at 25 deg C) To suggest that an mj15003 isnt fit for audio is not a very balanced view. Yes there are newer and better transistors. But that dosn't make everything that went before completetly useless.
I have heard many great amplifiers using those transistors. And im sure there are loads of people who visit this forum who have as well.
Sorry if I over reacted its just you hear so much over the top rubbish on forums sometimes it gets to me.
Or maybe its just thursday morning at work that is messing me up!
I have heard many great amplifiers using those transistors. And im sure there are loads of people who visit this forum who have as well.
Sorry if I over reacted its just you hear so much over the top rubbish on forums sometimes it gets to me.
Or maybe its just thursday morning at work that is messing me up!
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