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Electronics => Beginners => Topic started by: GnatGoSplat on August 10, 2012, 01:48:20 pm

Title: Understanding my transistor checker and transistor specs.
Post by: GnatGoSplat on August 10, 2012, 01:48:20 pm
I picked up a Chinese semiconductor checker for $17.99, it's just a bare PCB.  Pretty cool gadget, but I don't know enough about transistors to know what it's telling me.

I connected a KN3904 from my junk bin to it, it says hFE=205 Uf=790mV.  I know hFE is gain, but what does Uf mean?
I found this datasheet: http://www.datasheetcatalog.org/datasheet/kec/KN3904.pdf (http://www.datasheetcatalog.org/datasheet/kec/KN3904.pdf)
Under DC Current Gain, it has hFE(1), hFE(2), hFE(3), hFE(4), and hFE(5), none are anywhere near 205.  I also don't see a Uf spec anywhere.
Is it possible to even derive the specs listed in the datasheet from what my checker tells me, or is there not enough information?
Title: Re: Understanding my transistor checker and transistor specs.
Post by: grumpydoc on August 10, 2012, 01:57:12 pm
Quote
it says hFE=205 Uf=790mV

That will be Vf, I think - the collector-emitter voltage.

If you look at the datasheet you'll see that with a forward current of 10mA, and a forward voltage of 1V hFE should be within the range 100-300 so 205 is pretty typical for that device. Having said that we don't know what forward current your transistor tester put through the device, just that the measured hFE was with a VCE of 790mV.
Title: Re: Understanding my transistor checker and transistor specs.
Post by: Simon on August 10, 2012, 02:43:41 pm
Quote from: grumpydoc on August 10, 2012, 01:57:12 pm
Quote
it says hFE=205 Uf=790mV

That will be Vf, I think - the collector-emitter voltage.

If you look at the datasheet you'll see that with a forward current of 10mA, and a forward voltage of 1V hFE should be within the range 100-300 so 205 is pretty typical for that device. Having said that we don't know what forward current your transistor tester put through the device, just that the measured hFE was with a VCE of 790mV.

I think in your first statement you meant Vce
Title: Re: Understanding my transistor checker and transistor specs.
Post by: grumpydoc on August 10, 2012, 03:05:15 pm
Quote
I think in your first statement you meant Vce

Well, I'm guessing that the transistor checker was displaying "Vf" (or meant to) rather than "Uf" as reported in the first post so I stuck with that initially. But, yes, it should be VCE.
Title: Re: Understanding my transistor checker and transistor specs.
Post by: GnatGoSplat on August 10, 2012, 03:16:15 pm
Thanks, that would make sense considering it has several typos.  It also says "Unknown Devive" and spells resistor as "Resister".
Title: Re: Understanding my transistor checker and transistor specs.
Post by: OndraSter on August 10, 2012, 05:17:48 pm
FYI, in Czech ( I think that also Germans and surely some others as well) use U for voltage rather V.
Title: Re: Understanding my transistor checker and transistor specs.
Post by: GnatGoSplat on August 10, 2012, 06:35:52 pm
Ah, in that case, I'm sure that's the reason.  I think this board is based on Markus Frejek's design and I believe he is Swedish.
Title: Re: Understanding my transistor checker and transistor specs.
Post by: Mafdet on March 10, 2016, 01:49:58 pm
Sorry for digging up this ancient topic, but this is the first google result for "transistor Uf", so I suppose that many others who are looking for the answer are also going to stumble upon this post.

The correct answer seems to be: Uf=(Vf) forward voltage drop between the base and the emitter
For silicon transistors this is usually just below 700mV, whilst some of the germanium transistors (I've tested with a similar 'electronic components tester') Uf goes somewhere between 100mV and 200mV (OC74=~120mV) (OC79=~176mV) (OC44=~146mV).
This makes me wonder, since, to my understanding, they should be around 300mV. However, it's also possible that this 'tester' just doesn't work well with such -nowadays- rather rare components.

reference: https://www.darc.de/uploads/media/Transistortester_df1rn_rev_1.1_2013_03_11.pdf (https://www.darc.de/uploads/media/Transistortester_df1rn_rev_1.1_2013_03_11.pdf)
"Für das Beispiel von Bild 5 ist dies der Typ des Transistor NPN, die Zuordnung der Anschlüsse Basis, Kollektor und Emitter zu den Anschlusspunkten 1, 2 und 3, die Stromverstärkung hFE sowie die Basis-Emitter Flussspannung Uf in mV."

which roughly translates to:
"The example in image no. 5 shows an NPN-type transistor; the mapping of the pins 'base', 'collector' and 'emitter' to the tester connectors 1, 2 and 3; the amplification hFE as well as the base-emitter forward voltage Vf in mV."

(Since English isn't my native language and I'm still learning about Electronics, it may well happen that I mix up some of the terminologies.)
Title: Re: Understanding my transistor checker and transistor specs.
Post by: danadak on March 10, 2016, 02:27:12 pm
These might help -


http://www.aoc.nrao.edu/~pharden/hobby/HG_DS1.pdf (http://www.aoc.nrao.edu/~pharden/hobby/HG_DS1.pdf)

http://www.onsemi.com/pub_link/Collateral/AND9129-D.PDF (http://www.onsemi.com/pub_link/Collateral/AND9129-D.PDF)

https://www.youtube.com/watch?v=CsSemekf-K0 (https://www.youtube.com/watch?v=CsSemekf-K0)


Regards, Dana.