SemiSouth SiC Power JFETs

[Nrik]

Great. But someone should tell them we need some p-channels.

[StevenOH]

Guys, why is this "obsession" with the "complementary" devices/circuits?
Tubes designers never complain about their war chest. In fact, they are
very happy with what they can build.
Learn from them

[ingenieus]

When the silicon NPN power transistors (such as the 2N3055) came on the market, it was quite the thing to use in a circuit. It was years before any PNP matching device became available. Even then, they were very expensive. The only solution was the quasi-complementary output stage. A remarkable way to improve this was the amazingly simple Baxandal diode.

Once again we have an amazinge new device to play with, but in one polarity only. Does this mean that we have to look with new eyes at those quasi-complementary circuits again? I find this quite exciting. Now where can I find SPICE models for these thing?

[kipman725]

Amazing specs on the semi south parts gate charge is the same as 500V mosfets. A lower voltage switching version in a surface mount package is what would interest me. As for linear parts; if they cost so much already I would want a package that could withstand the maximum die temp to reduce/eliminate heatsinks, I wouldn't mind having to spot weld the leads if it came to it.

[kees52]

I have see that the semisouth are not real field effect transistors like the 2sk77 was, I have drawn a schematic of the yamaha b1 in multisim, but it do not work, in the time of that amp oscillations are a problem with these 2sk fets, I see that 2sk77 has -40 Vdgo while semisouth has far less negative voltage. a circlotron with semisouth is maybe possible, but gate drive is heavy so need a muscle driver.

[AKSA]

Yes, gate drive is heavy, at very high currents (32A) up to 220mA for Vgs of 3V from the SJEP120R100 datasheet. This requires a full on driver to overcome capacitance and current drive, and with availability of flat beta HV transistors with excellent SOAR I wonder if the high cost justifies their use. I guess you'd have to build and listen to be definitive about this; might be an application for low power Class A single ended.

Hugh

[kees52]

Originally Posted by AKSA

Yes, gate drive is heavy, at very high currents (32A) up to 220mA for Vgs of 3V from the SJEP120R100 datasheet. This requires a full on driver to overcome capacitance and current drive, and with availability of flat beta HV transistors with excellent SOAR I wonder if the high cost justifies their use. I guess you'd have to build and listen to be definitive about this; might be an application for low power Class A single ended.

Hugh

Hi Thanks, the old yamaha B1 has a reputation of a very nice sounding amplifier, with a real flied effect transistor, but was prone to faults of them, afcourse it is not fair so say that she are bad, but production methodes in that time was not comparable with technics we now have, chame, that commercial issieus are the reason of not producing them, tja, I am a sustainable man, excuse me.

The best solid state amp I have heard was with sanken ring emittors, driven with a super emittorfollower to lower impedance, it was almost 3D as the sellman say from a high end store, it has current feedback, (independent of bandwith and so fast), I am busy with a test with the same topologie with tube drive, I have test a lot of mosfets, the only way to get them nice sounding is big class a and quasi complementary or circlotron behaps, and then I have the feeling that bjt are still better if you chose wise, there are a lot of good ones out there, use high rail voltage is maybe also important..

I have here some sanken 2SC3264 and 2SA1295 who are big ones 200 watt dissipation, but not be made enymore for so far I now. 2 dn2540 I have made a cascode who go 70 v pp 0.03 % distortion 100 volts rail only two fets and no feedback, afcourse in a high ohms load, .

The J-fet power will maybe get back I have read, the 2sk77 has -40 Vgso voltage, the modern ones -15 to -20, I have seen the datasheet of the 2sk77, soo what close to a powertriode.

with power amps, there is so much idea,s and al are tested, the quality is liniar parts and no feedback, or only current feedback who is better as voltage feedback is my experience.

Z-transistors are very liniair and usable without feedback.

regards

[AKSA]

Agree about current feedback, Kees. Works very well, is fast, minimal compensation needed, comes back to devices.

I do think topology and operating point are the main determinants of sound quality, with devices chosen and layout having some influence.

I think the SemiSouth devices are not yet viable for audio, but that's just my 2c. Cost and availability does come into the equation.

You might examine the Constellation amplifier recently released from John Curl and James Bongiorno. It uses Quasi-comp outputs in bridge, using all npn devices in deep AB. Said to be wonderful sounding, with 2000W capacity into 2R.

Hugh

[kees52]

Good day

Australia is dark I think, be the way, I have some tryouts but after all, the modern mosfets are sound less good then bjt,s special with the sanken ringemitters who are very liniair, The End Milinnium amplifier use them, so far voltage amplifing with a tube gives the best results, the amp I have now playing here in home is the schematic shown below, but it is still sounding harsh, but not much, the semisouth simulation model I need for testing, she have audio transistors, but are not real field effect like I have tell you, but maybe use in a circlotron will work, I have a working schematic made with an extra driver mosfet, paralelling dn2540 will have then enough balls, two negative ccs can provide negative voltage, but the audio semisouth parts are normally off so here I need a normal way to do it, the real fieldeffect will never be made anymore in power version, it was the only tube like solid state in the 1980,s.

Only one thing I don,t understand is why I have a faseflip around 500 hz in the simulation (see pictures) it is coming from the tube voltage amp, maybe the mosfet follower do this but it is proberly the multisim itselfs who do this, it has still bugs.

And as last remark, ears of people are sooooo differend, but it is very interesting to hear what the differents are, I try to get music who has not the smallest harsh in it, and no hisss in the voices, but I have to keep in account that recordings are very important, so if you now some music cd,s who are good, I have superaudio NAD cd player, (repaired, the old 541i) maybe I put tube output in or a discrete all jfet amplifier as line amp, but jfets are less available these days also the small ones..

regards


Current feedback is independent of bandwith, and so it has far less impact on audio, only you need a offset control ic because it is not so stable as a voltage feedback amp who also control offset with it.

[kees52]

I have made a test circuit with semisouth, but with normally on ones, the for audio made ones has normally off, with ask a different approach and results are less good.


here with 200 watts, no feedback I have 0.007 procent distortion, the 4,7k pot works, the distortion can be adjusted,, the idea is from the yamaha B1 amp.

bandwith don,t need commenting, it is wel above 1 Mhz even without feedback.

If I put a valve for it, I have a simple hybride. the model I did made is possible not oke, I need a real one, I have fill in some things in a excisting 2sk170 model, like current, on voltage etc.

paralelling dn2535 wil give enough drive I think, it is still simulation..

regards