TO-3 BJT's

[weinstro]

Hi,

Quick questions.....

I'm looking at recycling an amplifier with Leach boards. The existing chassis is setup around TO-3 outputs. It looks like Toshiba, Sanken, and others have moved on to TO-3P packages.

Are there any interesting BJT's I should be considering, or is the MJ21193 pretty much the final chapter for the TO-3 package?

Also, I've noticed that ROHS compliant versions are being stocked. I don't plan on eating these, but are there any performance pros and cons to note for this version vs. the environmentally unfriendly version?

Finally, how consistent are the MJ21193/MJ21194 devices? i.e., if I want to match 12 devices within 5%, do I need to buy 13 or more like 130?

[AndrewT]

Originally Posted by weinstro

recycling an amplifier with Leach boards................. how consistent are the MJ21193/MJ21194 devices? i.e., if I want to match 12 devices within 5%, do I need to buy 13 or more like 130?

the standard Leach is a 2pair output stage.
You don't need to match 12 devices.
If you have 3 Leach amplifiers, then you need 3pair NPN and 3pair PNP.

What do you intend to match to 5%?

[weinstro]

Originally Posted by AndrewT

the standard Leach is a 2pair output stage.
You don't need to match 12 devices.
If you have 3 Leach amplifiers, then you need 3pair NPN and 3pair PNP.

What do you intend to match to 5%?

I was thinking about outputs.

I'm looking at 4 channels, and was going to increase the output devices to 3 pair per channel.

[jackinnj]

I have matched MJ15003/4 on my webstore -- I buy 100 at a time and match them for guitar guys -- they are pretty robusto.

[wg_ski]

Originally Posted by weinstro

Are there any interesting BJT's I should be considering, or is the MJ21193 pretty much the final chapter for the TO-3 package?

No, but the MJ21195 is. Maybe they'll come out with a 21197 some day, but it will just be a tweak to the process and still might only come out in the flatpack.

Also, I've noticed that ROHS compliant versions are being stocked. I don't plan on eating these, but are there any performance pros and cons to note for this version vs. the environmentally unfriendly version?

No difference in the TO-3 on the outside. The nonhermetic packages have a different finish on the leads and heat spreader.

Finally, how consistent are the MJ21193/MJ21194 devices? i.e., if I want to match 12 devices within 5%, do I need to buy 13 or more like 130?

You only need to "match" parallel sets - not all 12. If they're from the same batch (lot codes), they will be close enough for Vbe match. To be safe, I'd either buy one extra group of 3 in case you get remnants from standard tube quantities. To match Hfe, you need about 2x the quantity, but I never go to that trouble for emitter followers. Personally, I buy power transistors by the tube (either 25, 30, or 50, whatever is standard for that package) so they *will* come from the same lot.

[tiefbassuebertr]

Originally Posted by weinstro

Hi,

Quick questions.....

I'm looking at recycling an amplifier with Leach boards. The existing chassis is setup around TO-3 outputs. It looks like Toshiba, Sanken, and others have moved on to TO-3P packages.

Are there any interesting BJT's I should be considering, or is the MJ21193 pretty much the final chapter for the TO-3 package?

Also, I've noticed that ROHS compliant versions are being stocked. I don't plan on eating these, but are there any performance pros and cons to note for this version vs. the environmentally unfriendly version?

Finally, how consistent are the MJ21193/MJ21194 devices? i.e., if I want to match 12 devices within 5%, do I need to buy 13 or more like 130?

In this case I have started this threads:
bipolar (bjt) transistor families for audio power output stages
Threshold 800A and other old models: Mospec 2N5876/2N5878 or ON MJ21193/MJ21194 ?

[weinstro]

Thanks for all the responses.

Originally Posted by jackinnj

I have matched MJ15003/4 on my webstore -- I buy 100 at a time and match them for guitar guys -- they are pretty robusto.

Thanks - good to know. I'm several weeks from planning a purchase, but will keep this in mind. Is there any performance difference between MJ15003 and MJ21193?

Originally Posted by wg_ski

No, but the MJ21195 is.

I've compared the datasheets, and can't really point to major differences. The MJ21195 does appear to have more Ft fall off at higher Ic, though. In your opinion, why is the MJ21195 the superior device?

Originally Posted by tiefbassuebertr

In this case I have started this threads:
bipolar (bjt) transistor families for audio power output stages
Threshold 800A and other old models: Mospec 2N5876/2N5878 or ON MJ21193/MJ21194 ?

Thanks for the links, but the first seems to deal with mostly TO-3P devices, and I'm looking for TO-3's. Otherwise, I have to get into buying and machining heatsinks, which equates to time and money.

The second link discusses devices that appear to be obsolete. If these are still generally available, and there's a performance benefit with high-speed multi-emitter BJT's, I'm listening. If sourcing these is buying hand-fulls here and there, and worrying about matching and counterfeiting, I'll stick with the On-Semi TO-3s as the more headache free approach.

This kind of gets to the meat of the original question, though. Are those (probably obsolete) high-speed Japanese TO-3's worth it?

[tiefbassuebertr]

have you also see the new TO-3 series from ST?
http://www.st.com/stonline/products/...44/2st5949.pdf
as I know the highest value of Ft from currently production

[EchoWars]

Nice catch!

2ST5949 & 2ST2121, 250V, 17A, 250W, 25MHz

Very cool.

[wg_ski]

Originally Posted by weinstro

Thanks for all the responses.
Thanks - good to know. I'm several weeks from planning a purchase, but will keep this in mind. Is there any performance difference between MJ15003 and MJ21193?

I've compared the datasheets, and can't really point to major differences. The MJ21195 does appear to have more Ft fall off at higher Ic, though. In your opinion, why is the MJ21195 the superior device?

The 15003 is a MUCH older device type that can't handle as much voltage. They're still just as tough as the new ones when used within capabilities. Performance wise (beta, linearity, speed) it's a wash. The 21195 is just the most current 'version' of the 211xx. Overall, it tests just a bit better than the 93. The fT fall -off is likley within normal production tolerances.

Thanks for the links, but the first seems to deal with mostly TO-3P devices, and I'm looking for TO-3's. Otherwise, I have to get into buying and machining heatsinks, which equates to time and money.

What's killing the TO-3 is the heatsink machining cost and extra assembly steps that manufacturers want to engineer out of current products. You may already have heat sinks fitted for TO-3's, but unfortunately they don't come form the factory that way anymore.

The second link discusses devices that appear to be obsolete. If these are still generally available, and there's a performance benefit with high-speed multi-emitter BJT's, I'm listening. If sourcing these is buying hand-fulls here and there, and worrying about matching and counterfeiting, I'll stick with the On-Semi TO-3s as the more headache free approach.

This kind of gets to the meat of the original question, though. Are those (probably obsolete) high-speed Japanese TO-3's worth it?

I won't buy *any* power transistors that are not in current production unless I can get a couple in my grubby hands and pull the cover before buying a bunch of them. If you do find some genuine NOS (and can verify), and have the spare change, buy some because the chance may never come again. Having some on hand for repairs or one-of-a-kind builds is never a bad thing. But for a large build or new design, I'd say stick with what you know is good and can get reliably.