bipolar (BJT) transistor families for audio power output stages

Jump to Latest
tiefbassuebertr

tiefbassuebertr

Member
Joined 2005
tiefbassuebertragung.de
Bob Cordell said:
I was just comparing the devices that were mentioned here as being the same device, and where the japanese part was alleged to be superior. What are the more modern japanese transistors that you are referring to? I always like to do apples-apples comparisons.

BTW, I don't have the perception that Japanese data sheets are more complete or more accurate in their curves. Just look at the 2SC3264 LAPT datasheet; just one page.

Crappy or not, I have not been able to get SPICE models for many Japanese transistors.

My bottom line is that it is still usually dangerous to make generalizations, even though all of us are occasionally guilty of it.

Don't get me wrong. The Japanese do great things very well. I drive a Lexus and will probably never buy an American car again, although that is probably unfair on my part.

Cheers,
Bob
Click to expand...

By this thread is to see a curve tracer concept:
http://www.diyaudio.com/forums/solid-state/151253-diy-curve-tracer-pc.html
If it is possible to implement a appropriate software to get the p-Spice parameters about this curves, then one have a good precondition for more realistic simulation and comparable results. Additional I have a good tool to check the values of the manufacturer if he publishes it.
 
Last edited:
homemodder

homemodder

Disabled Account
Joined 2006
Bob, it could just be me, but Im quite happy with that datasheet, tells me enough of all the parametres of interest.

Tell me which spice models you looking for, I might have some that are of interest ,they have models but only release if you a regurlar buyer, from Sanyo Ive been able to get them to make me some for transistors I wanted and with a large purchase they supplied the models but in this they are very strict, their bussiness ethics differ quite a bit from ours. They state that spice models give out too many info on the part which doesnt make a lot of sense to me, surely one cannot make copies based on spice parameters.

As for the maths I think its important, only way we going to get better models, Andys output device models are the most accurate around this forum or any other for that matter, I dont use anything else. Ive spent some time modifying some models to closer reflect datasheet and I can tell you its not easy at all and very time consuming, a litttle change here to get this curve closer to datasheet and something else goes completly wrong with another parameter, Ive given up, I simply dont have the time.

Tiefbassuebertr, those mospec parts I wouldnt use, the chinese manufactured devices Im sorry to say are very inferior, they might have improved in the meantime but the first time I cracked a transistor of theirs open I was horrified. They also dont make up datasheets, they just supply a copy of the original manufactureres datasheet, scary, how do they know their parts are conforming to datasheet.
 
W

wahab

Member
Joined 2009
andy_c said:
Here's one other thought. Surely, the fact that fT varies with current indicates nonlinear behavior, right? But who's the culprit here? Let's imagine that Cbe were completely constant, independent of Ic and Vbe. Surely that's a requirement for linearity too. But equation (11) shows that for a constant Cbe and Ccb, fT is proportional to current! Indeed, the way to make fT independent of current is to arrange for Cbe to be proportional to current just as gm is. So the culprit of this variation of fT with collector current is the fact that gm is proportional to collector current.
Click to expand...

onsemi make the test using the following testbed :

(1) fixed frequency of 1 Mhz
(2) very low source impedance of 2R
(3) vce 5V in common emitter mode...

(1) implies that the Ft depend only
of the current provided this latter has a sufficent high value..
as the current is reduced, the Cbc influence increase , ending by
dominating the other significative factors in the gm constitution...

(2) and (3) implies that the Cbe is negligible, thus conforting the first
point, i.e ; Ccb as the main parasistic influence on the gm(I)..

this said, thank you for your explanation to my badly formulated
question..i should have said that the derivatives of the two curves we are
talking about are different, i.e , thus that dgm/dI are different for the two devices..( (delta gm)/(delta current)).....
 
W

wahab

Member
Joined 2009
to his credit, lumba expressed his views early on the thread,
that the japanese semis reign supreme and that the onsemi are crap,
at least for audio..
i can only agree, as why the heck would onsemi disseminate models
that show clearly that many of his products are old technology
rebranbded as new...
here we are comparing old toshiba devices that are no more in production,
to onsemi s current toshiba inspired flagships...
here curves of gain in emitter follower mode, the most used configuration
in audio amps, using currently produced devices...
the toshiba device is clearly better, with a margin that render pointless
critics about simulation...
 

Attachments

  • EF BW.zip
    4.9 KB · Views: 103
jan.didden

jan.didden

AX tech editor
Joined 2002
linearaudio.net
Paid Member
wahab said:
to his credit, lumba expressed his views early on the thread,
that the japanese semis reign supreme and that the onsemi are crap,
at least for audio..
i can only agree, as why the heck would onsemi disseminate models
that show clearly that many of his products are old technology
rebranbded as new...
here we are comparing old toshiba devices that are no more in production,
to onsemi s current toshiba inspired flagships...
here curves of gain in emitter follower mode, the most used configuration
in audio amps, using currently produced devices...
the toshiba device is clearly better, with a margin that render pointless
critics about simulation...
Click to expand...

Those graphs are from a sim, and are worth nothing unless you have checked that the models conform to the spec and data sheets.
Anybody seeing such nice flat curves should immediately mistrust them; they are too good to be real. Sorry.

jd
 
W

wahab

Member
Joined 2009
janneman said:
Those graphs are from a sim, and are worth nothing unless you have checked that the models conform to the spec and data sheets.
Anybody seeing such nice flat curves should immediately mistrust them; they are too good to be real. Sorry.

jd
Click to expand...

what interest us is not the absolute value, but the comparisons..
even the simulators is inncurate, it don t fail when showing that a device is better than another, whatever the error margin..

for the models, i used the manufacturers models so your critic
about them is irrelevant.

the test circuit is an emitter follower pair, the simulator has
no difficulties calculating the bandwith of a such simple circuit..

also, these curves have no trouble being flat, since the
scales are logaritmic, i.e, changing an exponential curve to a straight line..
 
B

Bob Cordell

Member
Joined 2006
cordellaudio.com
wahab said:
how those Ft curves are misleading..at first, i thought " how tricky is the
semi industry" , but in fact, it s me who was dumb, as figures speak for themselves..
the Ft curves display the gain AS A FUNCTION OF THE CURRENT, this, at a frequency of 1 mhz, thus showing no more than the gain dispersion as a
function of the current...
a perfect device would have a straight line...

no mention that their datasheet says 30mhz typ. at 1A ,the curves show 50MHZ+ at this bias point...mystery of the us industry..but let s take it as granted an discuss using the higher figure...

what you see as qualities for the MJL3281 are in fact serious drawbacks..
if we look at the curves, we see that from 0.1 to 2A, there s a gain
dispersion of 150%....
the 2SC3281 has a 50% dispersion in the same range, which tell that
it s three time more linear....at 0.01 A , his 0.1A gain is reduced by a factor of more than 4...
of course, onsemi did stop their curve at 0.1A, but extending it show clearly that at 0.01 A, their device has a gain close to 1....in fact, they display only
the part of the curve that is marketable...a key figure for amps designer is thus missing....
indeed, these curves tell absolutly nothing about the switching speed
or the bandwith of the product, despite their (misleading) name...
remember that 2SC is a more than twenty years old device, and the MJL
has increased current capacity and TDP compared to the original..
the question was to compare with the 2SC5200, the actual general
purpose bjts fo amps, but even then, the old toshiba device is better than
the onsemi one in an amp designer point of view, not adding that they are actually faster than the "modern one"....

the onsemi, as proved by the curves are not linear at all, not suited to audio, and are good at switching, as they have low gain at low current and gain increasing dramatically with the current...lumba ogir is right on this point...

attached are the gain curves in fuction of frequency with a 4A current, in common emitter mode for a 5V Vce...impedance source is 2R, so the
Cob influence is reduced to little value...


regards,

wahab
Click to expand...

Wahab,

It was a little unclear if you were also referring to beta droop of the MJL3281 devices in the post above, but I did do some measurements of beta on the MJL3281 at very low collector current to examine low-current beta droop. Here are the results, with Ic in mA on the left and beta on the right:

0.1 mA: 59
1.0 mA: 74
10 mA: 88
100 mA: 100
300 mA: 107

I consider these to be very good numbers for low-current beta droop in a large power transistor.

Cheers,
Bob
 
B

Bob Cordell

Member
Joined 2006
cordellaudio.com
homemodder said:
I agree no simulation is going to tell you anything about these parts but one thing is for sure Onsemi datasheets have errors, Bob you have much better equipment than me, compare the capacitances as stated by onsemi, actually the the p cob is much higher as it should be, given the structure, little datasheet errors, please also keep in mind you compairing 30 year old japanese component to a recent onsemi one, and overall one shouldnt forget that the onsemi is a 1302 with a little bit bigger die, so will obviously have better SOA but worse cob. I can think of more modern bigger die japanese transistors which are better if you want to compare apples with apples, here youll see better SOA than ONsemi with half the cob. Also youll notice that japanese datasheets are very very accurate unlike the western datasheets which are very optimistic sometimes, use curvetracer and do some comparisons and youll get interesting results.

Onsemi devices are not bad, they are copies of the japanese with much better quality control than like comparing chinese manufactured copies.

Through the channels I get the japanese devices the onsemi would cost me more than double the price, the US goverment still have heafty own industry protection taxation on goods coming in from japan, through the channels I use they are on equal footing and this way the japanese parts are much cheaper so it all depends on where you live and if your goverment is trying to protect your own industry, on level footing its a very different ball game.

Theres some interesting things written about ,,buy local practices,, still being used in the US.
Through tiefbassuebertrlinks you can get some details about the toshiba motorola onsemi marriage.
Click to expand...

Hi Homemodder,

What is an example of the more modern Japanese power transistor you have in mind in the post above?

Thanks,
Bob
 
You must log in or register to reply here.
Top Bottom