Pass XA.5 Concept

[Sipi]

Pronaci ce njega Bili...vidi, R8 se nalazi izmenju Katode (-) i Ref Pina...zato sam i zbunj....

Nece biti, katoda je ovde na plusu (TL431 ovde glumi zenerku...)

[sp300b]

Nece biti, katoda je ovde na plusu (TL431 ovde glumi zenerku...)

Nema druge

[Zen Mod]

samo vas gledam ........

[sp300b]

Nakon razmisljanja najblizi sam da u skoroj buducnosti malo ekperimentisem sa sledecom schemom uz nesto promenjene aktivne elemente

Vise detalja

pri cemu autor za ovaj UGS kaze:

To go straight to the conclusion, I must confess that (for me) this version is by (a lot of) far superior to the mosfet version, cascode or not.

Ultimate speed, added life to the music, truth everywhere, instrument location, dynamics, widening...

Wowwwww... What a beast !

And from the technical point of view, it's a pleasure. I love the elegant simplicity of the design.

And no more need of common-mode feedback resistors... Provided that the transitors are thermally coupled,

it sticks to 0V, typically 0.1 to 0.2mV, both relative and absolute, without any parts matching.

[BlueSky]

'Ajde !syn08 je poznat po tome da sve bolje zna i od Boga licno a Nelsona Pass-a ne bi primio ni za pripravnika Inace, sklonost TL431 ka samooscilovanju u nekim topologijama je siroko poznata i nema nikakve veze sa ovom pricom

Covek ima znanja bez obzira sto ume da bude arogantan. Inace, on napominje da se ne koristi ba

[Sipi]

Nakon razmisljanja najblizi sam da u skoroj buducnosti malo ekperimentisem sa sledecom schemom uz nesto promenjene aktivne elemente

Ne znam rode sta bi tu menjao, dasa ga je slozio tip-top, ta topologija ne moze bolje, jedino 2sk389 i 2sj109 zameniti sa dobro uparenim 2sk170 i 2sj74 (dupli JFET-ovi se mnogo tesko nabavljaju, a uoceni su i laznjaci) i umesto ZTX450/550 staviti BC550c/560c i to je to, dalje nema kud...

[Sipi]

[Zen Mod]

Nakon razmisljanja ......

dakle - sve se zavrsava ovde (naravno - uz tvoje poluprovodnike) :

[sp300b]

Ne znam rode sta bi tu menjao, dasa ga je slozio tip-top, ta topologija ne moze bolje, jedino 2sk389 i 2sj109 zameniti sa dobro uparenim 2sk170 i 2sj74 (dupli JFET-ovi se mnogo tesko nabavljaju, a uoceni su i laznjaci) i umesto ZTX450/550 staviti BC550c/560c i to je to, dalje nema kud...

Strasno, citas misli...diskutovao sam za Zenom popodne...uz sve sto si naveo jos 2SC4793/2SA1837 za strujna ogledala.

[BlueSky]

Ma covek je suvi genije - napravio u diskretnoj tehnici LM3886/TDA7294 i to samo sa duplo vise delova

No comment.

[sp300b]

[Zen Mod]

\dobio mail ..... razmisljam , kopam ;nedostaje ti par spojnih tacaka , a vrednosti cemo lako korigovati .svi kolektori vanjskog prstena tranzistora moraju biti raspolozivi napolju - propustio si par .sa tih tacaka se vodi signal na Vbe multiplier ili bias gene sa TL431javicu ti se kad nesto zdumam

[sp300b]

\dobio mail ..... razmisljam , kopam ;nedostaje ti par spojnih tacaka , a vrednosti cemo lako korigovati .svi kolektori vanjskog prstena tranzistora moraju biti raspolozivi napolju - propustio si par .sa tih tacaka se vodi signal na Vbe multiplier ili bias gene sa TL431javicu ti se kad nesto zdumam

U pravu si - korigovacu

[Manu]

I guys Very interesting thread ... I ll try to follow ... Manu

[sp300b]

Hi Manu. Btw - something like this...Changes of the element's value are highly possible.So far, no big thinking done around thisUGS_rev_A_schematic_04_06_2009.pdf

[sp300b]

rev B...UGS_rev_A_schematic_04_06_2009_rev_B.pdf

[sp300b]

[sp300b]

Da se ne zaboravi ...

Btw - odlicno objasnjenje za siroke narodne mase koje je sheff uradio.

nazalost na francuskom samo...za svoju dusu sam pokupio i google prevod na engleski, pa pokusavam da uklopim celu pricu...

[sp300b]

itd...

[sp300b]

Cascode

The cascode therefore, are BJT transistors inserted in series in the drains of the JFET. Their bases are maintained at a constant Voltage potential. As the potential of the base is constant (in the order of 10V for UGS), potential of the Drains will also be fixed, and 0,7V will be less than the potential of the bases. What makes that is ultimately drains the JFET will be at a constant potential. The VGS of JFET in normal operation is relatively low, we will quickly say that the VDS voltage at the terminals of JFET remained stable, or at least varies very little.

With this little trick we have three very interesting conclusions:

First, that the voltage of the JFET is within the 10V, that means we have reduced the power dissipated in the JFET: for example, for a current of 3.5mA, a JFET will dissipate 35mW, while without cascode, it should remove more than 65mW. It has therefore gained in overall thermal stability.

Second, as VDS is roughly constant, it will have the effect of linearization of the behavior of the JFET.

For an ideal transistor, the various "rights" to VGS = CSTE are parallel and slope zero. In reality, they are not, and the slope is not zero. So if the voltage of the drain JFET varies, the current drain of the JFET will also vary ... And where is the problem, you say? Well, is that we would like the current drain of JFET depends only on the input voltage, and not something else. (I remind you that had asked id = gm*vgs)

The cascode, setting the potential drain, thus to minimize this non-linearity, and working on a much closer these curves (in red zone ☺), where you can take that will variation of drain current negligible according to VDS.

Okay. Purists will tell me that VDS is to be maintained constant, and not only the drain voltage, as is done in the hope that the voltage source does not move too much. That's true. But I have not wanted to break the head, and you are free to try both versions, after all.

With all that, I forget to mention the last effect of the cascode, the extension of the bandwidth. B

[sp300b]

Details

[sp300b]

Potrebna mi je konsultacija.

Naime, razmisljajuci o disipaciji za XA.5 Concept, a uvazavajuci NP objasnjenje, te obzirom na tabelu datu u dokumentu Leaving class A, pokusavam da shvatim da li mogu na racun manje korisne snage (nesto tipa 25 W) da idem sa disipacijom od 100W (pricamo za jedan Mono kanal)?

Naime u svom Babelu imam hladnjake koji se regularno temperaturno ponasaju pri cemu trose 100W disipacije.

- Racunajuci na identicne hladnjake, koji bi to trebalo da budu moguci Naponi i biasi ?

Na kraju krajeva, ja sam nesto skontao da Pass u XA30.5 koristi plus minus 23 V, ali ne razumem bas sa kojim biasom?