Lumba Ogir said:
Let's see what we got here
No, transistors don't have a linear region. They have a region where the small signal approximation holds.
Variation of Gm with what? Which impedance? Maybe transconductance? Anyway, gm=Ic/Vt - always.
What is I/Gm? Why isn't it advantageous? Where did you get this from?
Nope, JFETs have generally larger voltage noise than bipolars. However, JFETs have virtually no input current noise, which is good for large source impedances, like a MM cartridge. Why do we use JFETs for MC? Because users were FUDed by "experts" that a few microamps through the coils are going to magnetize the whole cartridge. The same experts that recommend, for the ultimate sound quality, demagnetizing the vinyl LPs. The rest is convenience (self biasing, a few other details).
that's all I can say Not necessary for small signal devices.
Emitter degeneration (which, BTW, to your horror, is nothing but series in series out local negative feedback) does not reduce the gm. It trades gain for linearity, while gm is the same. Interesting enough, the gain of an emitter/source degenerated stage does not even depend on gm.
Everyone else, I just want to say that the most success we have had on this thread in the past few days is the knowledge given that the 2SA1084 and its complement, are available to you, and your friends at a reasonable price.
These are NOT perfect, but they are amazing devices, beyond the comprehension of certain 'experts' in semiconductor theory and design.
This is because these devices are very low noise, very low Rbb' (as low as almost anything) low input capacitance, high beta, high voltage, AND AVAILABLE at a reasonable price. Who could ask for anything more, except for maybe obsolete (not made any more) fets or special quality tubes ?
These are NOT perfect, but they are amazing devices, beyond the comprehension of certain 'experts' in semiconductor theory and design.
This is because these devices are very low noise, very low Rbb' (as low as almost anything) low input capacitance, high beta, high voltage, AND AVAILABLE at a reasonable price. Who could ask for anything more, except for maybe obsolete (not made any more) fets or special quality tubes ?
john curl said:
You did not disclose the part numbers, but only Hitachi as a manufacturer:
http://www.diyaudio.com/forums/showthread.php?postid=1829152#post1829152
Somebody else (Allen Wright) identified the exact parts:
http://www.diyaudio.com/forums/showthread.php?postid=1830124#post1830124
and you did not even 100% confirmed, but only a "maybe":
http://www.diyaudio.com/forums/showthread.php?postid=1830236#post1830236
It was me identifying a NA supplier for these parts:
http://www.diyaudio.com/forums/showthread.php?postid=1830824#post1830824
You did not even want to believe they are still available:
http://www.diyaudio.com/forums/showthread.php?postid=1831096#post1831096
Somebody else (Allen Wright) identified a supplier for Europe:
http://www.diyaudio.com/forums/showthread.php?postid=1831118#post1831118
Bottom line, your contribution about 2SA1084 and it's NPN counterpart was prety much what you always do for free. Thanks for nothing.
Just for clarity, just this afternoon, while lunching with my latest technician, I mentioned the thread, and said that although I did not get much real information, because most of the designs put forth are 20-40 years behind, comparable to my earlier efforts, I do learn new things, such as that the 2SA1084 is actually available these days. Last time that I checked, they were not available. Good thing to know, but I have about 100 of each device and I have no circuit where they would properly fit at the moment. However, it is the LINKS that many of you provide, that makes my effort worthwhile. Thanks again.
john curl said:
There is a special obsession in our technical culture with finding out who did what first and reminding everyone of it ad nauseam. For instance I'm sure Jim Williams would not complain if you pointed out Lord Kelvin did such and such first. You can probably bore yourself to death reading about how Steve Jobs lifted the MAC interface from Xerox PARC and at least a 100 persons views on what "really" happened.
OK, let us be precise about the 2SA1024 series of complementary devices.
Today, I found MY copy of the spec sheets that are about 30 years old. It was filed under Japanese transistors, but had been put aside, years ago, in fact it was SO OLD that it missed the firestorm that took 90% of my paperwork in 1991, as I had it filed in a dead file at my office rather than in my working file at home.
Yes, it is true that I forgot the exact number, AND it is not printed on the parts either. I can tell you what is on the part that should be the 2SA1024. It is: S5402, A E, 7J3 , ECB
These horizontal rows are arranged vertically over each other.
IS THE ANY QUESTION WHY I COULD NOT BE SURE OF THE DEVICE NUMBER, until I had finally found the device data sheet?
Now, these parts are so old, 30 years old, that they were almost forgotten, BUT I had evaluated them in the past, and they really were the best of kind devices I have ever found, including anything yet ventured here by anyone else.
I moved on to complementary j-fets for low noise design in 1981, so it didn't matter.
That's how old my info is, yet it as good, or better than virtually anyone here. I wish it were not so, so give me more real info, and I will thank you for it.
Today, I found MY copy of the spec sheets that are about 30 years old. It was filed under Japanese transistors, but had been put aside, years ago, in fact it was SO OLD that it missed the firestorm that took 90% of my paperwork in 1991, as I had it filed in a dead file at my office rather than in my working file at home.
Yes, it is true that I forgot the exact number, AND it is not printed on the parts either. I can tell you what is on the part that should be the 2SA1024. It is: S5402, A E, 7J3 , ECB
These horizontal rows are arranged vertically over each other.
IS THE ANY QUESTION WHY I COULD NOT BE SURE OF THE DEVICE NUMBER, until I had finally found the device data sheet?
Now, these parts are so old, 30 years old, that they were almost forgotten, BUT I had evaluated them in the past, and they really were the best of kind devices I have ever found, including anything yet ventured here by anyone else.
I moved on to complementary j-fets for low noise design in 1981, so it didn't matter.
That's how old my info is, yet it as good, or better than virtually anyone here. I wish it were not so, so give me more real info, and I will thank you for it.
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