Understanding my transistor checker and transistor specs. - Page 1
Forum section: electronics / beginners

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: August 10, 2012, 01:48:20 pm
content: 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.pdfUnder 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?

author: grumpydoc
author_rank: Super Contributor
timestamp: August 10, 2012, 01:57:12 pm
content: QuoteThat will beVf, 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 hFEshould 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 hFEwas with a VCEof 790mV.

author: Simon
author_rank: Unknown
timestamp: August 10, 2012, 02:43:41 pm
content: Quote from: grumpydoc on August 10, 2012, 01:57:12 pmI think in your first statement you meant Vce

author: grumpydoc
author_rank: Super Contributor
timestamp: August 10, 2012, 03:05:15 pm
content: QuoteWell, 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.

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: August 10, 2012, 03:16:15 pm
content: Thanks, that would make sense considering it has several typos. It also says "Unknown Devive" and spells resistor as "Resister".

author: OndraSter
author_rank: Contributor
timestamp: August 10, 2012, 05:17:48 pm
content: FYI, in Czech ( I think that also Germans and surely some others as well) use U for voltage rather V.

author: GnatGoSplat
author_rank: Regular Contributor
timestamp: August 10, 2012, 06:35:52 pm
content: 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.

author: Mafdet
author_rank: Newbie
timestamp: March 10, 2016, 01:49:58 pm
content: 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 dropbetween thebase and the emitterFor 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"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.)

author: danadak
author_rank: Super Contributor
timestamp: March 10, 2016, 02:27:12 pm
content: These might help -http://www.aoc.nrao.edu/~pharden/hobby/HG_DS1.pdfhttp://www.onsemi.com/pub_link/Collateral/AND9129-D.PDFRegards, Dana.