korben69 said:
jacco vermeulen said:
Actually the 2SJ109 is almost exactly the same as a dual monolithic version of the 2SJ74, and the 2SJ389 is almost exactly the same as a dual monolithic version of the 2SK170. The differences noted on the datasheets are very minor and can be ignored for the most part. For example, I think the P-channel dual monolithic is rated at 30 volts instead of 25 volts for the single part.
In the real world, there are some things to watch out for.
The most obvious thing is that the discrete parts will need to be matched by hand. This is not a problem for us as a manufacturer, as we purchase thousands at a time.
But the weird thing are the dual monolithic parts. There is a 7th pin connected to the substrate. If you try to ohm out the part and deduce the internal construction, it makes no sense. I have even asked FET designers, and they can't make sense of it either. The practical implication of the strange substrate construction and/or connection is that the dual monolithic parts seem to be very sensitive to static discharge. (Normally JFET's are very resistant to damage from static discharge.)
If you use them in the input circuit where plugging in a cable can introduce a static shock, they can fail. I have tried floating the substrate, tying it to ground, and tying it to the power supply rail. Nothing seems to help. So now I only use the dual monolithic parts in the "interior" parts of a circuit where they are not subjected to static discharges. (When the end-of-life was announced, we purchased something like 30,000 of each polarity! I figure we have a 15 or 20 year supply. Hopefully someone will make a replacement before then. If not, we can always just match the K170/J74 parts.)
jacco vermeulen said:
If you are talking about our new amplifier, the MX-R, that uses the ThermalTrak parts, thank you for the kind comments. We are very proud of that design.
If you are talking about the parts themselves, it turns out that they are very tricky to use. The example circuit in the app note is of little use. If you got it to work on one unit (by sheer luck), it wouldn't work on multiple samples due to tolerances in the parts.
Several people have tried to use them. My understanding is that McIntosh is using them, but in a rather odd way (at least to my way of thinking). They use the diode as a temperature sensor, but this signal is sent to a microprocessor that calculates the desired bias and applies it via a complex circuit. I don't like adding microprocessors, as the clock adds RFI to the circuit. We came up with a different approach, but it took several months of experimentation.
Hi Charles,
I do agree with you that microprocessors have no place in an amplifier circuit. M.L. take note.
For On Semi devices, I've been very impressed by the MJW0281A and MJW0302A parts. The ThermalTrak diode may be best used in a standard VBE multiplier.
I must apologize, I'm not familiar with your newer products - yet.
-Chris
I used to do warranty service for McIntosh in the 90's, and back then they seemed to stick to well designed audio circuits. It seems like Clarion's influence is being felt. Of course they may be searching for mis-adjustment proof products as the average quality of technician continues to spiral downwards.
I do agree with you that microprocessors have no place in an amplifier circuit. M.L. take note.
For On Semi devices, I've been very impressed by the MJW0281A and MJW0302A parts. The ThermalTrak diode may be best used in a standard VBE multiplier.
I must apologize, I'm not familiar with your newer products - yet.
-Chris
anatech said:
Those parts are the same die in a smaller physical package (TO-247) instead of the bigger MJL3281 and MJL1302 (TO-264). Unless you have radical space limitations, just use the bigger parts for a larger SOA.
Change the leading "M" to an "N" and you have the ThermalTrak parts. You can try a Vbe mulitplier. I try to avoid them when I can just on general principles, as they contain a (very short!) feedback loop.
There are lots of ways to skin this cat, but the important thing is to realize there are *many* sources of thermal drift, and each one must be compensated properly. A Vbe mulitplier tends to throw a blanket approach at two or three or four different problems, each with different time constants and thermal coeffiecients. Not the best, but usually workable....
Hi Charles,
I did test some samples and found those to have tighter matching of all specs. I know they are they same die. Could they have been selected?
I have some ThermalTrak parts which I've tested but have yet to use any in a circuit. Their pinout is one reason, can't just swap them in and out of working prototype boards.
As far as SOA is concerned, I'm not worried. About the highest power amplifier I'm likely to build would be 200W or less. Mostly 100W or less really. If I'm that close to the SOA, I'd add a couple devices. I understand where you are coming from though. You design production amplifiers. I experiment.
You would have my full and undivided attention when talking about these things.
-Chris
I did test some samples and found those to have tighter matching of all specs. I know they are they same die. Could they have been selected?
I have some ThermalTrak parts which I've tested but have yet to use any in a circuit. Their pinout is one reason, can't just swap them in and out of working prototype boards.
As far as SOA is concerned, I'm not worried. About the highest power amplifier I'm likely to build would be 200W or less. Mostly 100W or less really. If I'm that close to the SOA, I'd add a couple devices. I understand where you are coming from though. You design production amplifiers. I experiment.
Yes. You are correct. As I spend more time around here I tend to pick up little tricks. So possibly I'll learn sometime how to finesse this problem. For now I'm happy to have good sounding circuits without craters in the middle of the parts.
You would have my full and undivided attention when talking about these things.-Chris
anatech said:
The guy that designed the ThermalTrak parts (Mark Busier) improved the process for the power transistor dies with the result of much tighter matching. This improved process showed up first with the smaller parts you tried, and then the ThermalTrak parts. But all of the parts are now built with the improved process, for at least the last year or so. So you should see the tighter matching on all of these OnSemi parts.
Mr. Hansen:
Glad to see you around here! I don't mean to "put you back to work" so soon, but do you by any chance know of a suitable replacement for the RFG60P06 and IRCP054 devices? I am under the impression that such devices are not really available these days and these were items of a bygone era, but when I say that you popped up again, figured I'd ask
Glad to see you around here! I don't mean to "put you back to work" so soon, but do you by any chance know of a suitable replacement for the RFG60P06 and IRCP054 devices? I am under the impression that such devices are not really available these days and these were items of a bygone era, but when I say that you popped up again, figured I'd ask
Charles Hansen said:
I don't even need to cross the border to buy lots of either dually type in numbers of 50 to 25.000, with any production code ranging from '94 to '05.
For the less cunning/private persons overhere it's starting to make more sense to look for aluminium hat 2SJ73/2SK146.
At the start of the production of the 7-legged creatures, shop list prices were 1/4th of the 600mW duo in a pan.
The same shops that sold me the matched in a box types during your first Avalon model period still have a few leftovers right now, for close to the same rate as charged for the 3-year old obsoletes at the scarse place that still offers single number doubled JFETs.
Production cost of the last generation single and dual JFETs must have been very much lower due to the case standardisation and sticking two on a single substrate, at the cost of lower power handling and oddities.
Through my eyes, the Japanese discrete semiconductor industry has shown virtually no innovation over the last decade and a half, logic analysis points to possible successors as step-down and less versatile devices.
Chris,
i've got a lot of friends and relatives who belong to the dark side, they refer to something else when they talk about evil white S...
Hi Jacco,
Thank you!
Hi Charles,
I have noticed that trend from On Semi. This is exactly what was needed. Now, if we could only get On Semi making dual fets and some not expensive dual BJT's in a leaded package. A matched PNP and NPN in the same package would be really cool.
Looks like I should check some later samples. Most of the other numbers I received where all over the map.
If you know Mark Busier personally, give him a big thank you! His efforts have been noticed and are appreciated. I've been recommending On Semi parts as soon as I saw the MJW bits. If the others are as good now, that would be fantastic!
-Chris
LOL!
Thank you!
Hi Charles,
I have noticed that trend from On Semi. This is exactly what was needed. Now, if we could only get On Semi making dual fets and some not expensive dual BJT's in a leaded package. A matched PNP and NPN in the same package would be really cool.
Looks like I should check some later samples. Most of the other numbers I received where all over the map.
If you know Mark Busier personally, give him a big thank you! His efforts have been noticed and are appreciated. I've been recommending On Semi parts as soon as I saw the MJW bits. If the others are as good now, that would be fantastic!
-Chris
anatech said:
Mark had plans for a lot of things, including dual BJT's. I think the reality is that it takes a long time to bring these things to market. Mark is now only acting as a consultant to OnSemi. He has a company making Peltier refrigerators for pleasure boats, I think. But the audio program is still in action, and they are slowly adding things to the lineup. Mark's boss and the man still running the program is a guy named Todd Visconti. If you know any OEMs, please have send them to Todd and have them buy as much product as possible. The more they sell, the more cool products they will make!
luvdunhill said:Glad to see you around here! I don't mean to "put you back to work" so soon, but do you by any chance know of a suitable replacement for the RFG60P06 and IRCP054 devices? I am under the impression that such devices are not really available these days and these were items of a bygone era, but when I say that you popped up again, figured I'd ask
Both of those parts have been discontinued for several years. We found a replacement for one (I think it was the IRCP054) that was actually a better part, although without the current sensing pins. That's OK, because we can just set the bias by measuring the current through the rail fuse.
The problem is that part has also now been discontinued! We bought a few thousand just for repair stock.
If you have a V-3, just send it to the factory and we can fully update it. Call Michael at 303-442-7300 x223 and he can quote a price.
If you are building an amp from scratch, I would recommend using lateral MOSFET's such as the Exicon (Semelab) rather than vertical MOSFET's. Or better yet, the ThermalTrak bipolar outputs.
Hi Charles,
Actually, as I find cool devices I do make it known the best I can. I'm just a technician and can only yell so far. Still, every piece counts.
I am very careful not to abuse the samples program, but some people do. They've tightened it up to a point where ordering samples is sometimes not worthwhile.
If you get a chance to talk with either Mark or Todd, they need drivers and predrivers as well as signal devices. The predrivers would work in the Vas position as well. Surface mount devices are not welcome due to thermal issues. It's also a little difficult for small operations and hobbyists to get boards made for surface mount. Many commercial manufacturers I've seen do a very poor job of thermal modeling. It's also more difficult to thermally couple devices for tracking purposes.
Sometimes the old ways are the best. I don't mind working with surface mount stuff, just those occasions where leaded devices would be better.
Thanks Charles. You're lucky to be so close to the upper end of the supply chain. What are your thoughts on smt's?
-Chris
Actually, as I find cool devices I do make it known the best I can. I'm just a technician and can only yell so far. Still, every piece counts.
I am very careful not to abuse the samples program, but some people do. They've tightened it up to a point where ordering samples is sometimes not worthwhile.
If you get a chance to talk with either Mark or Todd, they need drivers and predrivers as well as signal devices. The predrivers would work in the Vas position as well. Surface mount devices are not welcome due to thermal issues. It's also a little difficult for small operations and hobbyists to get boards made for surface mount. Many commercial manufacturers I've seen do a very poor job of thermal modeling. It's also more difficult to thermally couple devices for tracking purposes.
Sometimes the old ways are the best. I don't mind working with surface mount stuff, just those occasions where leaded devices would be better.
Thanks Charles. You're lucky to be so close to the upper end of the supply chain. What are your thoughts on smt's?
-Chris
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