Hi,
Why not a LSK389 with zenners (to extend voltage rating) in the drain leads?
The current mirror is clamped. The input pair in it's own way too. It cannot see more than the positive rail voltage.
Ciao T
Why not a LSK389 with zenners (to extend voltage rating) in the drain leads?
The current mirror is clamped. The input pair in it's own way too. It cannot see more than the positive rail voltage.
Ciao T
IThose BC are different families (doping levels). They start as different processes (same line).
Family is: http://www.datasheetcatalog.org/datasheet/fairchild/BC547.pdf
BF family are definetelly different geometry...
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With BC types, A, B and C refers to gain group, not voltage, as it does on some BD types, e.g BD 249/250 - A=60V , B=80V, C=100V, D=120V, etc.
For low power but high voltage, consider BC 639/640 - not unlike MPSA 56/06, only higer Ft.
For even more voltage, think of 2N5551/5401 from Philips, these are rated at 150 Mhz, 160 V.
For high voltage and medium power, look at BF 471/472.
For high voltage and linearity like you wouldn't believe, take alook at medium powered BF 720/721 (they sell them at Farnell); the only caveat is the SOT-223 packaging, which si for SMT, so soldering tehm manually is a little more difficult than normal, but WELL WORTH the trouble. You could find that your open loop full power gain THD at 20 kHZ suddenly halves.
For medium power, the venerable old BD 139/140 set is still hard to beat, and you may want to look for them with extensions, like "-10" and "-16", indicating higher gain classes.
In the 30-50W class, it's no contest - Motorola's MJE 15030/15032 take the first prize. They are 160V, but there are lower and higher voltage versions.
Taking nothing (or at least not much) from MOH, in this case he missed prior art by about 20 years; but his detailed analysis and bringing the bootstrapped cascode and other topologies to the attention of the audio community is still appreciated. The first occurence I've found of the BC is from Aldridge, who applied the basic base current feedback back into the "lower" emitter to telephony amplifiers in 1962, in the first case to common-base stages; right after that an associate applied it to a topology where the first device is operated common-emitter with local feedback, which is now known as the MOH cascode. I discovered this recently and wrote of it in one of the Baxandall super-pair threads in here.
So it properly should be called the Aldridge cascode, not the Hawksford cascode. It is analogous to the other Hawksford topology with the complementary devices, the also-misnamed Larson/Baxandall-Swallow pair, invented and patent-applied-for by Frank Boxall in 1957 when he was an employee of Lenkurt, before he moved to HP.
Of course I am not suggesting that any of the later art was cribbed from the prior. The patent office missed Boxall when they granted Larson his patent (when he was at Tektronix, where it was called the super-alpha, according to John Addis), and Baxandall missed Boxall as well (he couldn't have known of Larson, as his piece applying the folded complementary pair to a current source, which has become eponymous as the Baxandall super-pair, was written while Larson's patent was under examination).
It's hard to do anything new!
Brad
T and bcarso are certainly correct.
The Japanese, at least up to now, have had a much better assortment of bipolar transistors and jfets, than either USA or Europe. Unfortunately, many really good devices (for audio) have been discontinued, leaving us to scramble to find nearly equal alternatives from what is still made.
Tvr's questions are virtually 'scary'! Please learn what voltage breakdown means with a bipolar transistor before applying one in a new situation. Learn what Vceo, Vcb, and Veb mean, and memorize their meanings. Remember, you usually don't have a second chance if you avalanche the transistor, and you MUST study the SAFE AREA of each and every power bipolar transistor, and please note that they are often expressed in LOG-LOG and are difficult to interpret casually without 'uncompressing' them by re-graphing or by very close study.
The best way to learn this is to study a series of data sheets (long form) from a major manufacturer, one after the other, to see the tradeoffs that are made for specific tasks. The best that I can personally recommend is to go to a used bookstore or the internet to get a 30-40 year old, or so Motorola Semiconductor Handbook, or one from another major manufacturer from that era, BEFORE home computers became available, and this was the only way to get the information necessary to design with a specific part. For example, you can find the 2N5551 bipolar transistor there with 5 pages of graphs and charts on that part ALONE. What a goldmine! All I can do is to suggest. '-)
The Japanese, at least up to now, have had a much better assortment of bipolar transistors and jfets, than either USA or Europe. Unfortunately, many really good devices (for audio) have been discontinued, leaving us to scramble to find nearly equal alternatives from what is still made.
Tvr's questions are virtually 'scary'! Please learn what voltage breakdown means with a bipolar transistor before applying one in a new situation. Learn what Vceo, Vcb, and Veb mean, and memorize their meanings. Remember, you usually don't have a second chance if you avalanche the transistor, and you MUST study the SAFE AREA of each and every power bipolar transistor, and please note that they are often expressed in LOG-LOG and are difficult to interpret casually without 'uncompressing' them by re-graphing or by very close study.
The best way to learn this is to study a series of data sheets (long form) from a major manufacturer, one after the other, to see the tradeoffs that are made for specific tasks. The best that I can personally recommend is to go to a used bookstore or the internet to get a 30-40 year old, or so Motorola Semiconductor Handbook, or one from another major manufacturer from that era, BEFORE home computers became available, and this was the only way to get the information necessary to design with a specific part. For example, you can find the 2N5551 bipolar transistor there with 5 pages of graphs and charts on that part ALONE. What a goldmine! All I can do is to suggest. '-)
Hi,
Pentodes date to the late 1920's IIRC and are basically hawkesford cascodes as their screen grids are (for AC) returned to the cathode in almost all cases (occasionally they are connected like ordinary cascodes, but that was considered bad practice in the 1930...
Cascoded triodes are probably as antique and usually also feature the AC return to the cathode.
Indeed.
Ciao T
Pentodes date to the late 1920's IIRC and are basically hawkesford cascodes as their screen grids are (for AC) returned to the cathode in almost all cases (occasionally they are connected like ordinary cascodes, but that was considered bad practice in the 1930...
Cascoded triodes are probably as antique and usually also feature the AC return to the cathode.
Indeed.
Ciao T
Hi,
For learning the Toshiba datasheets for 2SA970/2SC2240 include a complete set of H-parameter vs. Ic/Vce plots. Very instructive and about the most complete Transistor Datasheets I have seen.
Hence I prefer their use over some others, as I do not have to spend days with inadequate tools to generate the same data myself...
As Bob was fond of saying, the bits that you actually need to know about for a given device has been carefully excised from the datasheets...
Ciao T
For learning the Toshiba datasheets for 2SA970/2SC2240 include a complete set of H-parameter vs. Ic/Vce plots. Very instructive and about the most complete Transistor Datasheets I have seen.
Hence I prefer their use over some others, as I do not have to spend days with inadequate tools to generate the same data myself...
As Bob was fond of saying, the bits that you actually need to know about for a given device has been carefully excised from the datasheets...
Ciao T
Perhaps so, Thorsten, but most Japanese products are not readily available to me. My only alternative would be to stockpile them, and I'm kinda sick of doing that. It tends to suck up money like a vacuum cleaner.
Yes, BD 139/140 are very, very old trannies, but they still make for very convenient and good choices in some applications.
On the other hand, some of those actually old trannies somehow got lost, never got truly discovered for their true worth. BD 249/250 C are an excellent example. They have their voltage limitations, not to be used with more than +/- 40V, but otherwise truly outstanding on sound and robustness. The SGS Thomson version can deliver current peaks of 50 A.
They are often confused with TI's TIP 35/36 C, and while similar and obviously originating from the same roots, they are NOT the same. Even a short look at the TI Data Sheet book will show the BD series to be considerably faster than the TIP series (shorter Ton, Tstore and Toff).
I understand SOA, but one needs to get in the ballpark first. Even I know a transistor won't last very long if you put 110V across a 40V transistor. I also have new direct experience seeing how some rather surprising voltages can show up where one does not expect them from simple faults.
What I find on the WEB is usually the short, or very short version. ( one page), or the long version for parts we can't buy. Of the graphs available, part to part from different vendors tend to have different charts, so I have not had much luck guessing which are the most relevant. The same apparent graph from different manufactures are frequently quite different. About the only general conclusion is no part is very linear in any parameter, but I knew that. A blanket statement "Japanese are better" or "study the charts" I easily accept as wisdom, but not quite as useful from this end as it could be without a place to start.
So, looking for a hint. Say a 2SA1514/2SC4102 over a KSA992/KSC1845. What SHOULD I be looking at? If I were pick them for the IPS? (Ok, I know, you want me to look at FETS there anyway, but let's just say BJT) What graphs would suggest I run them at 1mA vs. 2mA bias for example? 2 inch square charts are a little difficult to have much value.
What I find on the WEB is usually the short, or very short version. ( one page), or the long version for parts we can't buy. Of the graphs available, part to part from different vendors tend to have different charts, so I have not had much luck guessing which are the most relevant. The same apparent graph from different manufactures are frequently quite different. About the only general conclusion is no part is very linear in any parameter, but I knew that. A blanket statement "Japanese are better" or "study the charts" I easily accept as wisdom, but not quite as useful from this end as it could be without a place to start.
So, looking for a hint. Say a 2SA1514/2SC4102 over a KSA992/KSC1845. What SHOULD I be looking at? If I were pick them for the IPS? (Ok, I know, you want me to look at FETS there anyway, but let's just say BJT) What graphs would suggest I run them at 1mA vs. 2mA bias for example? 2 inch square charts are a little difficult to have much value.
I second the motion!
Not just because JC says so, but because I still own Data Sheet books from Motorola and TI from pre-1980. The data offered there is far more comprehensive than anything I have seen to date, from anyone.
This is my gripe with Japanese transistors - I may have been unlucky and may have missed some really good sources, but I find their data sheets to be, at the very best, scarce. This I find very surprising, given that the Japanese are generally very meticulous, even pedantic.
Just take a peek at Motorola's data sheets for MJ 15024 and such like power devices - when you see any new Data Sheets, from anybody, which are even remotely as extensive and thorough, please let me know.
Dejan,
If you can finesse the imports on your side, I can probably get you samples for an IRC and arrange production qty's at sensible prices. Heck, you could even make money bringing stuff like that into your corner of the world...
They made a poor choice IMHO ca. 1985 and my opinion of them has not improved since. Of course, I remember the eastern block, where you had to make a virtue out of noy being able to get the parts you needed and still had to make things work...
Again, I use them and their like (I do specify a lot of BC... and TIP... Parts) because I know them. My fault entirely.
I usually find better suited parts a few month later on some japanese website. I guess a decade from now I'll only specify Japanese semis... I'm a slow learner.
Ciao T
If you can finesse the imports on your side, I can probably get you samples for an IRC and arrange production qty's at sensible prices. Heck, you could even make money bringing stuff like that into your corner of the world...
They made a poor choice IMHO ca. 1985 and my opinion of them has not improved since. Of course, I remember the eastern block, where you had to make a virtue out of noy being able to get the parts you needed and still had to make things work...
Again, I use them and their like (I do specify a lot of BC... and TIP... Parts) because I know them. My fault entirely.
I usually find better suited parts a few month later on some japanese website. I guess a decade from now I'll only specify Japanese semis... I'm a slow learner.
Ciao T
Even the 2SA970 is not listed on Toshiba's pages, but the 965 is, so let's go there for a moment. Short pages, only 6 charts. Pretend I was going to use it for what they recommend, a driver. Looking at their SOA chart, I am good for Ic of several mA at 100V. Looking at Ic-Vbe it is not very linear until 100mA or so, which would imply I need to be operating at under 10 volts to be very well behaved. For roughly the same voltage, current, frequency and power, this part is not far from the 2N5401, yet it has 5 times Cob. What is that telling me?
Why is it "your fault", Thorsten?
Don't they do the job you took them for well enough?
Are you sure a Japanese transistor would do the same job audibly better?
If I was asked the above question, I think I'd say offhand that sometimes, perhaps they might, other times no.
I never liked the general market Japanese audio from the 70-ies. It sounded hyped up to me, made to appear very powerful, yet when facing a more complex load, ready to give up very soon.
Over the years, I have exchanged a fair lot of Japanese TO-3 power devices from that period, you will remember that more powerful plastic pack trannies only started appearing in the late 70ies. Given that I can procure only Motorola power devices and be sure I am getting Motorola's parts and not some Foo Manchoo China parts, I naturally gravitated towards them.
And let me tell you what I got to hear - in EACH AND EVERY case, no exceptions, a simple exchange of trannies for Motorolas, WITH NO MODIFICATION of the protection circuits, there was never one single amp which did not sound from better to a hell of a lot better.
Not to even mention what happened to those complex loads when the protection circuitry was adjusted to accomodate for much more powerful devices - as it should be, since I took out 90 and 120 W devices and pushed in 250 W devices. Let's just say that the differences in their SOARs was, er, notable.
Don't they do the job you took them for well enough?
Are you sure a Japanese transistor would do the same job audibly better?
If I was asked the above question, I think I'd say offhand that sometimes, perhaps they might, other times no.
I never liked the general market Japanese audio from the 70-ies. It sounded hyped up to me, made to appear very powerful, yet when facing a more complex load, ready to give up very soon.
Over the years, I have exchanged a fair lot of Japanese TO-3 power devices from that period, you will remember that more powerful plastic pack trannies only started appearing in the late 70ies. Given that I can procure only Motorola power devices and be sure I am getting Motorola's parts and not some Foo Manchoo China parts, I naturally gravitated towards them.
And let me tell you what I got to hear - in EACH AND EVERY case, no exceptions, a simple exchange of trannies for Motorolas, WITH NO MODIFICATION of the protection circuits, there was never one single amp which did not sound from better to a hell of a lot better.
Not to even mention what happened to those complex loads when the protection circuitry was adjusted to accomodate for much more powerful devices - as it should be, since I took out 90 and 120 W devices and pushed in 250 W devices. Let's just say that the differences in their SOARs was, er, notable.
It tells you that the prophets of this world were from Japan.
They were the first to catch on to the fact that to profit, you need to make something LOOK like it's the Real Deal, when in fact it could be quite common.
Which is certainly NOT to say that the Japanese have never produced any really great trannies, even in high power devices, which is their weakest spot because they treat transistors as tubes, and in doing so, accept some of the tube weaknesses. Current was never their strong point, although they have come a long way since.
http://www.semicon.toshiba.co.jp/docs/datasheet/en/Transistor/2SA949_en_datasheet_091221.pdf
Unless they have some secret, paying customer set of data sheets, I am not learning much from this.
Unless they have some secret, paying customer set of data sheets, I am not learning much from this.
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