How to Test Transistors with a Multimeter - NPN, PNP, JFET
HTML-код
- Опубликовано: 18 июн 2019
- Using a digital multimeter in diode test mode, we can check NPN and PNP transistors to see if they have semiconductor junctions in tact, and we can also identify which pin is emitter, collector, and base.
Using diode check mode along with a resistance measurement, we can also check if a JFET appears to be functional.
If you'd like to support the channel, you can:
Support me on Patreon: / gadgetreboot
Shop through my affiliate links!
Banggood www.banggood.com/custlink/3vK...
Aliexpress s.click.aliexpress.com/e/_AFeHwB
Amazon.com www.amazon.com/?&_encoding=UT...
Amazon.ca www.amazon.ca/?&_encoding=UTF...
Videos are mirrored at LBRY/Odysee: odysee.com/@GadgetReboot:4
#ElectronicsCreators
Background music from the RUclips music library:
A Rising Wave by Jeremy Blake
Ridge Racer by DivKid 
Наука
Thank you for this, you have helped me identify some 1978's soviet PNP transistors. You explained this very well and the part when you said the higher voltage drop that is the emitter made things a lot easier.
Cheers!
Well Explained Video For A Person Without Any Electronic Experience
This is one of the best explanations I've seen on RUclips! It will help me immensely to troubleshoot a guitar pedal!
This old engineer appreciates the refresher or what you might call a sanity check!
Very informative. I am not a tech but I am a DIY guy repair a stereo received. I appreciate your teaching style. I found 2 bad transistors! Thanks!
This is actually prefect timming for some projects I got cooking thanks!!
Very well made video, wish I had this info back in high school (30+years ago). Much love from 🇨🇦 Canada
Excellent and easy to follow explanation. I've watched others on tis subject, but they went too fast and I got confused. No such problem here though. Liked and subscribed.
Excellent tutorial, for easy understanding. The jfets part has a very good explanation.
Good stuff. Thanks for the refresher.
You have a very good skill when explaining this. Congrats on the video! You have helped me in my studies!
Thanks a lot !! I had bought a jfet from aliexpress, no way to have the exact datasheet, thanks to you I could figure out the pinout.
thank you very much for your video, it clears my doubts since I am putting together a small inductance meter circuit and in this circuit a (JFET) is included in the design, I am not very familiar with this specific Semiconductor but thanks to your video I am clearly learning from him, thanks a hug, 🤝🎩🚭
Excellent job explaining and showing testing!
Thank you very simple and understandable.
Finally found a good way to test FETs, in circuit tested iffy so I out on my semi conductor tester tested ok, but when I do a meter check it shows a short. Great video and explanation.
You made this super easy. Thanks so much.
Thank you. Very clear and interesting!
Best video on testing electronic elements
Very informative tutorial, been very helpful in determining npn, pnp and finding the emitter, base and collector.
Thanks providing this. Good job!
Thank you so much for this video. It is helping me help a fellow ham repair an old electronic keyer. 73! Bret C/AC0AE
This is a best video regarding this subject to n RUclips. Excellent work 👏👏
Very helpful video
Really good one, have trans tester but this is much faster :)
Thank you for the video
nicely explained clean simple easy to understand
very helpful indeed thanks for sharing
awesome video thanks for the refresher it's good to see this again after all these years
Excellent explanation sir...... It's so helpful
Thank you for explaining in enough detail for an enthusiast to comprehend.
Nice. Thank you. I guess I always thought about this back when I was in college.
wow, thx. i learned it from you. best description.
One of the first little projects I soldered together was a circuit from a Mims III book that tests NPN and PNP transistors but of course it doesn't work for JFETs or MOSFETs.
This is awesome. Thanks mate
Thank you for the useful video
Very helpful thanks!
Exactly the bag of tricks I need for recycled parts! 😎
thank you
you are the best
Creative video,thanks :)
Exelent video tks 🎩
Very helpful! Some guy from Serbia made very quality video as this one. So common People can easily understand.
THANK YOU SO MUCH
Fantastic
Those are handy facts and tips about BJTs and JFETs. thank you very much.
Thanks for the info .. do those values change if transistor is in a circuit ?
Very good description of the behaviour of NPN and PNP transistors. Looking at your diode representation of a NPN, is it true to say (without getting into the internals of the transistor) that when a small current is supplied to the Base, that the diode representation for the Collector/Base effectively switches around to be aligned with the diode representation of the Emitter/Base so that current flows between the Collector and the Emitter. If this isn’t the case, then with your diode representations, how can current flow between the Collector and the Base. Hope this makes sense
if you read the paragraph called “function” on this Wikipedia article a few times it might help explain it.
en.wikipedia.org/wiki/Bipolar_junction_transistor
it all has to do with the physics of the transistor geometry such as the base area being thin and the emitter being more heavily doped with charge carriers and how electrical momentum can be created to allow current flow between the emitter and collector.
Thanks
Nice, but how to test power NPN's with inner diode like BUL58D. Should the base - emitter both directions be in short while dialing while base collector can be dialed only one direction?
thanks
Can you also suggest a testing method for in-circuit transistors?
Not all multi-meters will give an indication of junction voltage.
A better method is to put the lead supplying the +ve voltage on the collector and the other lead on the emitter. Then touch the collector and base with fingers and a working NPN transistor will conduct. Swap polarity for PNP transistors.
Thank you for being able to speak English.
I'm fluent in that and gibberish
Hello there! I really like the video, you must be a very patient guy. I have a problem with measuring and it makes me unsure. On the scheme I have NPN transistor, yet it tests like PNP, also E & C check positive on continuity test, however I haven't de-soldered them from the PCB. Should I just remove them?
sometimes the component does need to be removed from a circuit to test properly because other things can interfere with measurements.
This is one of the best explanations I have come across on this topic. I already knew how to test NPN and PNP transistors but did not know how to test JFET transistors. I have a few 2SK30A R transistors that I removed from a circuit and want to test. In the diode mode they tested fine, but when I tested in resistance mode with Gate and Source grounded the reading was around 550 ohms. Would that figure be considered too high since you mentioned a couple hundred ohms max resistance. Is there a benchmark figure where it can safely be assumed that the transistor is faulty. I am just a DIY trying to get a better understanding of electronics. Thanks for sharing your knowledge.
I haven't worked with JFETs enough to have direct experience observing failures and all the sources I have seen refer to "a few hundred ohms" as normal with gate source connected, so it seems subjective but 550 ohms sounds close enough to good. I think a bad one would more likely have damage on the gate from excessive voltage, so if the diode check works, I'd say it's all good.
@@GadgetReboot Thanks for your swift response.
Please do a video about how buzzer works on pcb, especially where the buzzer get feedback from.
Great video. Why are you not using the DC voltage setting when measuring the voltage value between the Base and Emitter and Base and Collector for the NPN transistor? You use the coninuity setting.
when the transistor is not in a powered circuit there is no voltage to measure but since the base to emitter and collector behave like diodes, the diode check can be used and the meter provides the power for that. if I was using continuity mode I was just checking to see if the transistor has a short circuit and if it does there would still be no voltage to measure if it were powered up.
Great video. I have an SMD 2n5457 which measures drain-source resistance of approx 315 ohms - would you say this is a defunct JFET?
A couple hundred ohms is normal when the fet channel is fully conducting, so as long as it goes up very high toward infinite resistance when the channel is closed, it would seem to be working fine.
@@GadgetReboot thanks. You are a scholar and a gent.
I have a transistor that I suspect has gone bad. It tests okay with the DIMM, but the ESR meter shows an hFE of 735 or so and according to some information I found online its hFE should be between 800 to 1500. Does that mean it is indeed bad and has to be replaced? Thanks.
My (cheap) multimeter in diode mode does not show voltage drop, it shows resistance in Ohms (in 400-500 range for good diodes) - can I use that reading for anything useful besides finding a short ?
Be aware that the leads on an _analog_ multimeter have reverse polarity for such tests. That is, the red lead is negative and the black lead is positive battery. If that 's confusing, simply swap the lead connections on the meter for the purpose of this type of test.
I take it that is the case with some analog multimeters and not all multimeters because it seems a bit of a wierd thing to do and I'm not exactly sure why you would do that. When I connect my red probe to be delivering voltage and current that is exactly where I expect it to be coming out of, not switching around.
It would actually be a very bad design the more I think about it now, all it would do is add to confusion.
Great video another subject on Transformers DTA/DTC DTC114ES transformers in my schematics i am working on a repair they are listed as IC's i am confused the data sheet i have found show in out and ground with built in resistors.
I am probably taking wrong readings at this point but cant find any good videos on these
why is it you will sometimes see a reverse voltage of a volt or so?
how do we know it is either drain or source gate? from what you did you only show when we already know the left pin is the drain. how do you decide it is the drain pin?
One way to tell the difference is if there is different behaviour when shorting the possible drain with gate compared to shorting possible source to gate. The gate-source voltage is what controls the conducting channel, where zero volts (a short) from gate to source will open the channel and give low drain-source resistance.
So if we measure low drain-source resistance with gate to pin A but then high resistance when shorting gate to pin B, then pin A must be source because we were able to open the channel.
Is there a way test them if you don't have a diode check mode on your multimeter?
The easiest thing would probably be to get another meter, even $10 or less on Amazon I have seen a meter that not only does diode check but it also directly can test certain transistors at least NPN and PNP.
in my case: I insert multimeter: red(+) in base [mid pin] - and - black(-) first or third pin, and contacts[show in multimeter],... NPN 2N3904 - E-B-C = in this case, E or C can be used interchangeably???
emitter and collector aren't interchangeable
Do they have to taken out to test them ?
Hello..im thinking of replacing a transistor labelled 'ST C945 G G2'..can you please suggest what kind of transistor and the exact euivalent i can use safely?Im repairing an old cambridge soundworks amplifier..thanks!
i’ve never seen the part number before but it looks like a general purpose NPN that can be replaced with other general purpose, the ones commonly available to me are 2N2222 and 2N3904. of course use the information at your own risk but that’s the best information I can find on those numbers. envirementalb.com/c945-transistor-pinout/
transistor looks the same . how do know if this component BJT or JFET
Is this true when the transistor is in-circuit?
what if i ave voltage drop between emmiter and collrctor?
What does it mean if I only get 1 reading from the transistor..?
Shout out idol
How do you figure out if it's jfet or just transistor if it's blown? I'm working in a old printer. It was reverse polarity blown. 6 volt printer with 12 volt reversed charger. I have a few to fix but I can't find any info With what is printed on the component.
if it’s blown so that it’s got open or short connections then measuring it won’t work but if you can see the markings then you can try to look up various codes. There’s a lot of different websites about surface mount component markings like
alltransistors.com/smd-search.php
for through hole parts this might help www.qsl.net/yo5ofh/doc/transistor_codes.htm
Great job. I wonder why they can't just write the data on all tranistors though. P N P, etc. How hard could it be? In fact I do not understand why they don't do it. I mean it can't be just because they don't like to make things easy. Can it?
It wouldn't surprise me.
I have some 30+ year old ceramic disc capacitors that have the exact value stamped on it like "0.1uF" and I thought that was like finding a unicorn. I'm afraid to use it in a breadboard in case I break the leads
@@GadgetReboot lol. Maybe stick them in real bread, then don't forget to take themout and put them into a fresh loaf before it hardens, otherwise you'll break the legs off!
Seriously though, I do find the world of electrics electronic magnetism, you name it, bleeding confusing. Universal system??? It doens't exist, that would be too simple. Make a farad huge, that way we'll be dealing with millionths of em, make an amp enourmous, that way when 2 kills someone it'll seem less serious., don't label transistors as that would be telling. Call an amp I, after intensity, just in case anyone was getting to grips with it.
It's a bit like yOutube, don't allow viewers to watch the video as they scroll the comments as that would be useful. But then youtube/ google have just dropped the bomb on Blogger. It wasn't broken, so of course they 'fixed it' with a new version that's 'mobile friendly'. Show me the moron that writes 2000 words blog posts on his mobile phone (while walking through traffic, or a park, or at 'work') and I'll show you 2000 words of crap.
Great old user platform, dumped for some simpistic moron useful crap. No labels on transistors, tu m'etonne(what a surprise!
Take it easy dude
Can you test all this, in board?
The two top videos when searching "testing transistors with multimeter" are this and Markusfuller's video. He says the exact opposite. He says for an NPN you should get a reading with negative lead on the base and positive on the collector. I'm so damn confused.
I just watched the other video and he said NPN gets a reading with positive on the base while PNP gets a reading with negative on the base. But his transistors have different pinouts with the base on the end instead of center pin.
Thank you so much. I was losing my mind trying to figure out which was correct. @@GadgetReboot
At the end of my comment when I said “ how can current flow between the Collector and the Base”, I meant “how can current flow between the Collector and the Emitter”
Can a transistor give the Ebike more speed
I'm still confused about source and drain terminals, how to recognize them properly with DMM?
when measuring the resistance between drain and source, when the gate is floating the resistance is probably going to be very high up in the megs, but when measuring the resistance drain to source and gate is also shorted to the source, it’ll be lower resistance, in this case it was a couple hundred ohms.
So which ever pin shorted to the gate leads to a lower resistance reading from drain to source, that pin that’s shorted to the gate must be the source.
But how we can say that it's source or drain?
if you don’t know what any of the three pins are, you do the diode test to figure out where the gate is because it will have a diode drop from that pin to the other two pins.
when you know which pin is the gate, measure resistance across the other two pins which will be source and drain, and do it while connecting the gate to one of those pins and then the gate to the other of those pins.
when you see the lower resistance reading, the pin connected to the gate at that time is the source pin.
Thanks a lot 👍👍
I hqve q circuit which needs 2n3819
I cannot find 2n3819 so Can i exchage 2n3819 with 2n5457??
If it's a general circuit, substituting might work as mentioned near the bottom of this page where a bunch of common part numbers are mentioned for substituting www.muzique.com/lab/splitter.htm
@@GadgetReboot its a peizo pre amp.. alexrice peizo pre amp..if u take a look
www.zachpoff.com/resources/alex-rice-piezo-preamplifier/
Thankyou for reply
Request transistor Fet J111.
Is jfet actually mosfet?
they are different in enough ways to be considered unique more than interchangeable.
Not working for me 🤨
Got a J201 & BC547
Zero reading
At 0:38 Im lost after that.
nefunguje to! pre transistor npn 3399 , c114 , pnp A1345, bez testera to nezistis !
I observe you are blocking the video with your hand....while placing the leeds....
One day I aspire to have an elaborate multi camera setup and better video editing skills