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?
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?
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.
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.
No difference in the TO-3 on the outside. The nonhermetic packages have a different finish on the leads and heat spreader.
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.
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?
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?
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?
wg_ski said:
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?
tiefbassuebertr said:
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?
have you also see the new TO-3 series from ST?
http://www.st.com/stonline/products/literature/ds/14244/2st5949.pdf
as I know the highest value of Ft from currently production
http://www.st.com/stonline/products/literature/ds/14244/2st5949.pdf
as I know the highest value of Ft from currently production
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.
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.
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.
Nope, completely missed it in one of your posts cited above - thanks!
Looks like it's available at Digikey for ~$3 ea. This could work.
I wonder what Cob is and what ft at 5A falls to? The specified value is at 1A.
Toshiba's version says 270 pF. As far as fT fall-off, it will follow similar curves to all the triple diffused types.
Funny, the Toshiba C5949 isn't in a TO-3. I wonder if ST or Fairchild will put a 5200 in a TO-3 can?????? One can only hope. They're available in 4 different plastic packages. What's *missing* is the 3281/1302 from ON in a TO-3, but the demand isn't there.
Well, ST carries a TO264 version of that one too: ST 2STC5949. I find it a bit surprising that ST chose to make their clones also available in the metal can package; it's kind of rare seeing modern devices put in TO3 cans nowadays.
However, something looks fishy if you compare the SOA plot to the original: Toshiba 2SC5949. What's up with the SOA, especially the pulsed curves, at high voltage? Is it a typo, more safety margin, or is it really that much worse compared to the original? I'm not saying it's unusable, it looks very useful still, but it might not be suitable for directly substituting 2SC5949. More importantly, this difference in the datasheet makes me wonder how comparable they are in the other specs.
Isn't this ST device very close to what a 3281/1302 device in a metal can would be, assuming that the 2SC5949 and 2STC5949 chips are comparable? I had a look at the Toshiba 2SC3281 and Toshiba 2SC5949 datasheets and they are almost exactly identical; the only difference I found was that the thermal resistance is lower for the 2SC5949. I'd guess the 2SC5949 is essentially a 2SC3281 chip with the same die solder thickness improvement that allowed them to use a smaller chip in the 2SC5200 without sacrificing power rating as compared to the 2SC3281.
However, something looks fishy if you compare the SOA plot to the original: Toshiba 2SC5949. What's up with the SOA, especially the pulsed curves, at high voltage? Is it a typo, more safety margin, or is it really that much worse compared to the original? I'm not saying it's unusable, it looks very useful still, but it might not be suitable for directly substituting 2SC5949. More importantly, this difference in the datasheet makes me wonder how comparable they are in the other specs.
Isn't this ST device very close to what a 3281/1302 device in a metal can would be, assuming that the 2SC5949 and 2STC5949 chips are comparable? I had a look at the Toshiba 2SC3281 and Toshiba 2SC5949 datasheets and they are almost exactly identical; the only difference I found was that the thermal resistance is lower for the 2SC5949. I'd guess the 2SC5949 is essentially a 2SC3281 chip with the same die solder thickness improvement that allowed them to use a smaller chip in the 2SC5200 without sacrificing power rating as compared to the 2SC3281.
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