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'[EE]:Vce(sat) -Hfe, was Protecting FETs'
2002\10\15@081228 by Alan B. Pearce

face picon face
>I happened to have the datasheet for the BD203, and took a look at the
>specs.
>
>Ic = 4A, Vce = 4volts : hfe min=20, hfe max = 100
>Ic = 10A, Vce = 4volts : hfe min=5
>
>Ic=4A, Ib=400mA : Vce(sat) max = 1.1volts
>Ic=10A, Ib=3.3A : Vce(sat) max = 8volts
>
>That dosen't seem particularly good, in fact the Zetex seems to be better?

I suspect that what Roman actually measures is well at the "top" or "good"
end of the range. I suspect that if you compare the Zetex transistors with
anything else in a similar size package then they really are "super
transistors". But if space is not a problem then using something like a
BD203 may well be better, but it is far from comparing like with like, more
like comparing crab apples with golden delicious.

Certainly the specs that Michael listed (as quoted above) are about what I
would expect a manufacturer to publish for a device like a BD203,
considering it's age and technologies available then. It may be that Roman
is able to source units still using this part number which have had process
modifications to their manufacturing process to keep the production spec
nearer the upper "desirable" limits of Vce(sat) and beta.

However I would not want to be using 10,000 BD203 transistors based on the
saturation voltage/Hfe tests Roman has done, and relying on all devices to
meet it. One day you will end up with a batch with Vce(sat) of 1.1V at Hfe =
10.

We all leap down the throats of people here who suggest using a PIC outside
it's operating spec after all.

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2002\10\15@142500 by Roman Black

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face
Alan B. Pearce wrote:
>
> >I happened to have the datasheet for the BD203, and took a look at the
> >specs.
> >Ic=4A, Ib=400mA : Vce(sat) max = 1.1volts

That sounds NOTHING like the BD203's i'm using.
Which again is why I never trust the specs, and
only trust specs and brands I have tested.

{Quote hidden}

OK, I do deserve a slap for suggesting relying on
out of spec performance. But they perform as they do,
and given that I always test any batch purchased
before using in a project I have no qualms about
using them for their (observed) low sat performance.
It's not like exceeding Vceo or Ic spec etc. YMMV. :o)
-Roman

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2002\10\16@023038 by Russell McMahon

face
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face
* Delayed 12 hrs due to email hiccup*

Ah -still in outbox - I'll grab the new better subject line.

> Zetex (or Farnell) seem to have deliberately
> chosen to show a beta of 160, at a totally
> unreasonable current for a 3A transistor. When
> operated as a low-sat transistor the beta is
> VERY POOR.

Are you SURE you have the pinout right on your Zetex parts ????
I imagine you almost certainly have BUT they do have a strange case and
unusual pinouts. They may just be providing that Beta while reverse polarity
:-) !!!!

Also, there are Zetexes and Zetexes alas.

The table at http://www.zetex.com/3.0/b1-2.asp
provides very precise statements about what you should be able to expect.
And it's not what you are getting !

eg  ZTX1047A E-line
Vceo = 10V (low!)
Ic max continuous = 4A
Hfe 300-1200 @ 1A
       240-1200 @ 4A

Vsat 70 mV at 1A at 10 mA Ib = Beta of 100
Vsat 190 mV at 4A at Ib = 20 mA = Beta of 200 !!!!!!!!

ZTX1048A seems similarly blessed with Vceo = 17.5v (how precise :-) )

Certainly many (most?) are worse than these specs and the results get
generally worse with higher Vceo but there are some good specs there and
Zetex themselves are very open about the spec.


Here's the equivalent 30-50v table

       http://www.zetex.com/3.0/b1-6.asp

The frabjous FCX890B in SOT89 seems to have the best of all worlds except,
no doubt, price :-)
Vceo = 45V
2A max cont
400 beta min at 1A
150 beta min at 2A
80 mV sat at 100 mA at Beta = 200
300 mV sat at1A at Beta = 200

Even the FZT1049A in SOT223 is no slouch at
30 V Vceo
330 mV Vsat at 5A with beta = 100
That's  a bright LED !!! :-)

Zetex, by the way, are located in the UK within easy reach of the Lake
District.
Once known AFAIK as "Newmarket Transistors" long long long ago.

Pictures of 47 year old transistors

       http://ourworld.compuserve.com/homepages/Andrew_Wylie/newmark.HTM



       RM

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2002\10\16@031128 by Roman Black

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face
Russell McMahon wrote:

> > operated as a low-sat transistor the beta is
> > VERY POOR.
>
> Are you SURE you have the pinout right on your Zetex parts ????

Ha ha ha! That's rule number 1 of being a TV
repairer - insert parts the correct way around! ;o)

> The table at http://www.zetex.com/3.0/b1-2.asp
> provides very precise statements about what you should be able to expect.
> And it's not what you are getting !

Actually I downloaded the Zetex datasheets for the
parts I have and the datasheets backed up my test
results.


> eg  ZTX1047A E-line
> Vceo = 10V (low!)
> Ic max continuous = 4A
> Hfe 300-1200 @ 1A
>         240-1200 @ 4A
>
> Vsat 70 mV at 1A at 10 mA Ib = Beta of 100
> Vsat 190 mV at 4A at Ib = 20 mA = Beta of 200 !!!!!!!!

Now THAT is a transistor I would have been
delighted with!

> The frabjous FCX890B in SOT89 seems to have the best of all worlds except,
> no doubt, price :-)
> Vceo = 45V
> 2A max cont
> 400 beta min at 1A
> 150 beta min at 2A
> 80 mV sat at 100 mA at Beta = 200
> 300 mV sat at1A at Beta = 200

Again a dream compared to the ones I bought.
I chose parts from the Farnell catalogue and
bought some PNP Zetex that were supposed to be
"high performance" like the ZTX951. I will have
to check out some of the "better" Zetex parts as
you said. Unfortunately they don't stock the
ZTX1047A or FCX890B you mentioned.
-Roman

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