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Thread: Protecting FETs
www.piclist.com/techref/index.htm?key=protecting+fets
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face BY : Russell McMahon email (remove spam text)



> > > > I should e-mail RS and find out exactly what they mean by Vce
> > > They won't know.
> > I e-mailed the UK office anyway. When / if I get a reply I'll pass it on

>                        Dear Sir,
>                                In reply to your enquiry relating to the
> transistor tables and quotes of Vce .The lines for hfe Ic/mA and Vce
should
> be read together . Such that the gain value hfe is quoted at a particular
> value of collector current and collector to emitter voltage .
>                                                     Regards ,
>                                                     John Taylor.

That would be almost convincing if your list of 3 examples had not included
the entry

       2SC3329 Vceo 80     Vce 0.1

Now it's POSSIBLE that they are intending to state the hfe with the
transistor saturated but I rather doubt it. I suspect that John Taylor has
made a valiant attempt to explain what he sees.

Another possible explanation, also without perfect correlation with reality,
is that this parameter is MEANT to be Vebo. I looked at the relevant table
in the RS catalogue and, with that theory in mind, chose a device with a
very high figure for Vce. The Zetex ZTX600B has a claimed Vce of 10 and a
look at http://www.zetex.com shows it also has a Vebo of 10 volts. Not conclusive
but suspicious. [[With a Beta of 1,000 minimum at 1A this E-line (TO92
sized) part should be kept in mind for impossible applications. Vsat at
0.85v at 1A is high as it's a Darlington]].

But aaaagh - it does have it's hfe specd at Vce=10v ! :-)

As one last try - the MJD127 has an RS Vce of 1 volt but at
onsemi.com.cn/pub/Collateral/DataSheet/mjd122rev1.pdf
they list no parameter at 1 volt. It does have a Vce_sat of 2v. (Warning -
this is a pdf AND if you read it they will probably have to kill you)*.


           Russell McMahon


* - read url

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