O.K. I just looked at the Faichild offerings in 300-500V devices. I only found 1 with the transcunductance like we might be after. The others were 3 or 4 times higher? There were some things like thermal resistance which in some cases were unbeleiveably low. Probably a big die! and with that will be big capacitance! About double ussually!
As I was saying, the 16N25C is a great choice
As I was saying, the 16N25C is a great choice
FLG,
Have you read the link above about the discontinuation of the original parts, specifically the refernce ti the P chaanel performance. I assume his statement can be taken in context of using the 19n20c complimentary part. If this is a safe assumption, it seems safest to try to match the performance of those parts. To look for unique replacements opens up too many variables in this case. I have some of the newer parts, which happen to have higher yfs, with the transfer curv epushed over in such a way as to test charles' theory. I will post measurements on all, but point for point, i think the 16n part is the closest we may come to the original in performance when viewed within the context of th eleast amoun to fpossible changes. I am going to read the Hansen thread again, as he was a lateral fan, as am I. The IRF9240 hump may or may not be present with this Fairchild part.
Have you read the link above about the discontinuation of the original parts, specifically the refernce ti the P chaanel performance. I assume his statement can be taken in context of using the 19n20c complimentary part. If this is a safe assumption, it seems safest to try to match the performance of those parts. To look for unique replacements opens up too many variables in this case. I have some of the newer parts, which happen to have higher yfs, with the transfer curv epushed over in such a way as to test charles' theory. I will post measurements on all, but point for point, i think the 16n part is the closest we may come to the original in performance when viewed within the context of th eleast amoun to fpossible changes. I am going to read the Hansen thread again, as he was a lateral fan, as am I. The IRF9240 hump may or may not be present with this Fairchild part.
I will join in and say Realy great that you are taking the time with this.
And that is the main thing
I have noticed the pool and will abstain from voting as I have been using FQP19N20 with FQA12P20 since last August
As I have made no comparrison, sound wise, with other devices I can not express any constructive opinion.
Still To me it does sound like one of the best amplifier I ever Had.
IMO FQA19N20L would be baad as it may match worse with Positive counterpart.
If I may.. Why not ask Papa for help?
I am shure that once he is avvare of your (most laudable) effort he may chip in whit same advice.
There may be other avenues as on PM keep that between us for now.
Papa has been asked, but I would not be surprised if he doesn't answer. He wants us greedy boy'z to figure somethings out. Hopefully there will be some insight, but i think it is possible that we can over-think this. Without some anomaly in the response like in the thread mentioned by FLG concerning IRF P channel parts, we should get pretty decent performance from this part based on what we see in the datasheet. I think it may be possible to offer FQP alternatives for those who desire them, but I would like to stay with larger form devices for sake of heat and ease of use. Especially with diode version of F5T, we are dealing with some settings that are going to be sensitive to heat level and having bigger and more easily cooled parts may help somewhat. That being said, BKsabath is proof the other works. Kudos to him for branching out with the different part.
Buzzforb, it is possible that Charles's comments were 5 years ago before the introduction of some of the parts we are seeing today? It didn't really look like his enference was true. But, what he was emphasising seemed to be transconductance P-N matching? Right?
We don't have that in any pair we play with except the 1530/201. We seem to be focused on matching capacitance or something otherwise?
We don't have that in any pair we play with except the 1530/201. We seem to be focused on matching capacitance or something otherwise?
Why isn't FQA16n25C in the list to vote on? Is there a typo in the list?
I will go with what ever you guys decide.
Papa did give the nod to the Toshiba 2SJ200 2SK1529 early in the Turbo thread. They had lower capacitance than the larger 2SJ201 2SK1530.
Rush
One thing I noticed with the comparison of the 19n20c part with the 19n25c part was the difference in the drain-source on resistance, Rds(on). 0.14 Ohms vs 0.22 Ohms respectively.
Has anyone done any measurements or modelling of this, or even have any thoughts? The P-channel 12p20 has about 0.36 Ohms on resistance, so maybe you are right buzzforb and the 19n25c is a better match.
Hi Buzzforb,
You wrote on the other thread (post #166) that you had some samples on the way and were going to compare the FQA16n25c with the orginal 19n20c part. That comparison will give you so much more useful information than I could ever gain from reading the datasheets that I am perfectly willing to follow your advice, whichever part you end up choosing.
I understand your financial dilemma and hope it helps to say my order stands (as long as the costs do not skyrocket, of course) whichever part# you ultimately decide is best.
Thanks for your effort in getting this done right!
Albert
You wrote on the other thread (post #166) that you had some samples on the way and were going to compare the FQA16n25c with the orginal 19n20c part. That comparison will give you so much more useful information than I could ever gain from reading the datasheets that I am perfectly willing to follow your advice, whichever part you end up choosing.
I understand your financial dilemma and hope it helps to say my order stands (as long as the costs do not skyrocket, of course) whichever part# you ultimately decide is best.
Thanks for your effort in getting this done right!
Albert
Buzzforb, it is possible that Charles's comments were 5 years ago before the introduction of some of the parts we are seeing today? It didn't really look like his enference was true. But, what he was emphasising seemed to be transconductance P-N matching? Right?
We don't have that in any pair we play with except the 1530/201. We seem to be focused on matching capacitance or something otherwise?
It is like to the EUVL approach to the output stage. The fets he chose have natural complimentary characteristics. Because of this, they should show better cancellation and lower distortion without any help. He has tried to reproduce this in the front end with the different degeneration resistors on the Jfets, trying to balance the curves there. Fortunately we have P3 to help achieve this same thing in the F5T. I too looked again at alternatives from Fairchild, but only found stuff that came close at the cost of a very large increase in Ciss and differnces in other areas as well. If you want to look though the EOL stuff, go to Rochester Electronics and type in FQA.
Yes, exactly correct. But the toshiba parts were designed to be a complementary pair. IR, Fairchild and the rest in that line were not. I beleive Papa does not use the Tosh's due to the unobtanium aspect and the 'ol "I've got buckets of them" probably still holds true for IR and Faichild parts.
Rds(on) refers to devices which are fully opened (when used as switches, On or Off).
In an audio power amplifier, the output devices are variable resistance devices.
At idle, DC-trimpots balance the resistance values of P- and N-channels, NFB adjusts the power device impedance beyond that.
Zhou Fang was still operating a few weeks ago. As ussuall, you'll have to wait. I think after a couple weeks I tried again and he set me up and shipped. I think it only took a week to get here. I actually wanted the BA-3 transistors but had to look somewhere else for those.
I think I saw something about only shipping every 2 weeks or something. He also has raised P-N matched Tosh pairs to $45!!! due to lower stock. It might be wise to pick up a few 1530/201 pairs before it really gets difficult and more expensive. I did.
I think I saw something about only shipping every 2 weeks or something. He also has raised P-N matched Tosh pairs to $45!!! due to lower stock. It might be wise to pick up a few 1530/201 pairs before it really gets difficult and more expensive. I did.
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