How to Test Transistors with a Multimeter - NPN, PNP, JFET

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  • Опубліковано 18 чер 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.
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  • Наука та технологія

КОМЕНТАРІ • 114

  • @Dinco422
    @Dinco422 17 днів тому +3

    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!

  • @sanditroup7634
    @sanditroup7634 Рік тому +4

    This is one of the best explanations I've seen on UA-cam! It will help me immensely to troubleshoot a guitar pedal!

  • @maximum7904
    @maximum7904 22 дні тому

    Well Explained Video For A Person Without Any Electronic Experience

  • @MichaelPuente
    @MichaelPuente 3 роки тому +4

    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!

  • @johncronk1338
    @johncronk1338 2 роки тому +2

    Very well made video, wish I had this info back in high school (30+years ago). Much love from 🇨🇦 Canada

  • @waynegnarlie1
    @waynegnarlie1 3 роки тому +3

    This old engineer appreciates the refresher or what you might call a sanity check!

  • @percyhornickel
    @percyhornickel 2 роки тому +1

    Excellent tutorial, for easy understanding. The jfets part has a very good explanation.

  • @GeorgeJFW
    @GeorgeJFW 5 років тому +4

    This is actually prefect timming for some projects I got cooking thanks!!

  • @juddery
    @juddery 2 роки тому +5

    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.

  • @brannonjones3668
    @brannonjones3668 Рік тому

    Excellent job explaining and showing testing!

  • @sand0077
    @sand0077 4 роки тому +6

    Very informative tutorial, been very helpful in determining npn, pnp and finding the emitter, base and collector.

  • @TiagoSantos-dp9rl
    @TiagoSantos-dp9rl 10 місяців тому

    You have a very good skill when explaining this. Congrats on the video! You have helped me in my studies!

  • @dannyyorri2345
    @dannyyorri2345 4 роки тому +4

    Thank you very simple and understandable.

  • @keithstone001
    @keithstone001 2 роки тому +1

    You made this super easy. Thanks so much.

  • @loicplayer
    @loicplayer 4 місяці тому +1

    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.

  • @sailorguy9288
    @sailorguy9288 Рік тому +1

    Best video on testing electronic elements

  • @DrexProjects
    @DrexProjects 5 років тому +1

    Good stuff. Thanks for the refresher.

  • @ReyciclismoMTB
    @ReyciclismoMTB Рік тому

    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.

  • @ELECTROxigeno76.
    @ELECTROxigeno76. 2 роки тому +1

    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, 🤝🎩🚭

  • @taddy666
    @taddy666 2 роки тому +1

    Thank you. Very clear and interesting!

  • @BretChilcott
    @BretChilcott 2 роки тому +1

    Thank you so much for this video. It is helping me help a fellow ham repair an old electronic keyer. 73! Bret C/AC0AE

  • @terrymorgan7885
    @terrymorgan7885 5 років тому +2

    awesome video thanks for the refresher it's good to see this again after all these years

  • @opikok6183
    @opikok6183 2 роки тому +1

    Thanks providing this. Good job!

  • @themlotproductions
    @themlotproductions 3 роки тому +3

    Thank you for explaining in enough detail for an enthusiast to comprehend.

  • @charlesnijanthan3686
    @charlesnijanthan3686 2 роки тому +1

    Excellent explanation sir...... It's so helpful

  • @jedandecko5585
    @jedandecko5585 5 років тому +1

    Really good one, have trans tester but this is much faster :)

  • @pukyalligator
    @pukyalligator 2 роки тому +1

    wow, thx. i learned it from you. best description.

  • @CirYdnar
    @CirYdnar 2 роки тому

    Nice. Thank you. I guess I always thought about this back when I was in college.

  • @RadioFixer
    @RadioFixer Рік тому

    This is a best video regarding this subject to n UA-cam. Excellent work 👏👏

  • @tossancuyota7848
    @tossancuyota7848 9 місяців тому

    nicely explained clean simple easy to understand

  • @keivn91
    @keivn91 8 місяців тому

    Exactly the bag of tricks I need for recycled parts! 😎

  • @shyammohabir8283
    @shyammohabir8283 3 роки тому

    very helpful indeed thanks for sharing

  • @electronic7979
    @electronic7979 5 років тому +1

    Very helpful video

  • @stormz4040
    @stormz4040 4 роки тому +1

    Thank you for the video

  • @HazeAnderson
    @HazeAnderson 5 років тому +1

    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.

  • @user-vs9du7xv7m
    @user-vs9du7xv7m 11 місяців тому

    This is awesome. Thanks mate

  • @nazeerabdulrahuman9526
    @nazeerabdulrahuman9526 Рік тому

    Thank you for the useful video

  • @My6stringer
    @My6stringer 6 місяців тому

    Thanks for the info .. do those values change if transistor is in a circuit ?

  • @dialnfornick
    @dialnfornick Рік тому

    Very helpful thanks!

  • @Columbariusify
    @Columbariusify 2 роки тому +1

    Very helpful! Some guy from Serbia made very quality video as this one. So common People can easily understand.

  • @youriklaassens7198
    @youriklaassens7198 5 років тому +1

    Those are handy facts and tips about BJTs and JFETs. thank you very much.

  • @Bianchi77
    @Bianchi77 Рік тому +1

    Creative video,thanks :)

  • @muradghazzawi5088
    @muradghazzawi5088 5 років тому +1

    thank you
    you are the best

  • @ELECTROxigeno76.
    @ELECTROxigeno76. 2 роки тому +2

    Exelent video tks 🎩

  • @FellDestroyedMusic
    @FellDestroyedMusic Місяць тому

    THANK YOU SO MUCH

  • @theprogrammerrolandmc3039
    @theprogrammerrolandmc3039 4 місяці тому

    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

  • @ilyaluv6186
    @ilyaluv6186 2 роки тому

    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?

  • @markustg09
    @markustg09 2 роки тому

    Can you also suggest a testing method for in-circuit transistors?

  • @techcimbi2050
    @techcimbi2050 2 роки тому

    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?

    • @GadgetReboot
      @GadgetReboot  2 роки тому

      sometimes the component does need to be removed from a circuit to test properly because other things can interfere with measurements.

  • @hanahawlokam351
    @hanahawlokam351 3 роки тому +1

    Thanks

  • @sprinter768
    @sprinter768 2 роки тому

    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.

  • @yaseenhashim8538
    @yaseenhashim8538 4 роки тому +1

    thanks

  • @marcus9x9
    @marcus9x9 3 роки тому +1

    Fantastic

  • @georgiosyiannakou734
    @georgiosyiannakou734 10 місяців тому

    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.

    • @GadgetReboot
      @GadgetReboot  10 місяців тому

      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.

  • @fomalhaut9
    @fomalhaut9 4 роки тому +1

    Great video. I have an SMD 2n5457 which measures drain-source resistance of approx 315 ohms - would you say this is a defunct JFET?

    • @GadgetReboot
      @GadgetReboot  4 роки тому

      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.

    • @fomalhaut9
      @fomalhaut9 4 роки тому

      @@GadgetReboot thanks. You are a scholar and a gent.

  • @laytonjames9741
    @laytonjames9741 2 роки тому +1

    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

    • @GadgetReboot
      @GadgetReboot  2 роки тому

      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.

  • @clevc112
    @clevc112 3 роки тому +1

    Thank you for being able to speak English.

  • @dmitripogosian5084
    @dmitripogosian5084 2 роки тому

    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 ?

  • @ihyaulumuddin1711
    @ihyaulumuddin1711 2 роки тому

    Please do a video about how buzzer works on pcb, especially where the buzzer get feedback from.

  • @ska757
    @ska757 3 роки тому

    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.

    • @GadgetReboot
      @GadgetReboot  3 роки тому +1

      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.

    • @ska757
      @ska757 3 роки тому +1

      @@GadgetReboot Thanks for your swift response.

  • @neddyladdy
    @neddyladdy 4 роки тому +1

    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.

  • @TondipeaMaskedMaster
    @TondipeaMaskedMaster Рік тому

    what if i ave voltage drop between emmiter and collrctor?

  • @phreaktor
    @phreaktor 2 роки тому

    why is it you will sometimes see a reverse voltage of a volt or so?

  • @BadRonald1
    @BadRonald1 2 роки тому

    Do they have to taken out to test them ?

  • @gonfreecs2212
    @gonfreecs2212 2 роки тому

    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!

    • @GadgetReboot
      @GadgetReboot  2 роки тому

      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/

  • @NoBetterTech
    @NoBetterTech 3 роки тому

    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???

    • @GadgetReboot
      @GadgetReboot  3 роки тому

      emitter and collector aren't interchangeable

  • @timmyvlog9379
    @timmyvlog9379 4 роки тому

    transistor looks the same . how do know if this component BJT or JFET

  • @larrybud
    @larrybud 3 місяці тому +1

    Is this true when the transistor is in-circuit?

  • @ThePupil
    @ThePupil 9 місяців тому

    Can you test all this, in board?

  • @James_Bowie
    @James_Bowie Рік тому

    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.

    • @Ghost572
      @Ghost572 Рік тому

      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.

  • @JesseHoff
    @JesseHoff 3 місяці тому

    Is there a way test them if you don't have a diode check mode on your multimeter?

    • @GadgetReboot
      @GadgetReboot  3 місяці тому

      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.

  • @laytonjames9741
    @laytonjames9741 2 роки тому

    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”

  • @azmansamat5221
    @azmansamat5221 3 роки тому +1

    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?

    • @GadgetReboot
      @GadgetReboot  3 роки тому

      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.

  • @clydecare
    @clydecare 2 роки тому

    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.

    • @GadgetReboot
      @GadgetReboot  2 роки тому

      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

  • @haroldkortwright8502
    @haroldkortwright8502 Рік тому

    Can a transistor give the Ebike more speed

  • @Silva-yq3sf
    @Silva-yq3sf 19 годин тому

    Request transistor Fet J111.

  • @ceasarsalad2388
    @ceasarsalad2388 2 роки тому

    What does it mean if I only get 1 reading from the transistor..?

  • @Netlife-001
    @Netlife-001 3 роки тому +1

    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.

    • @GadgetReboot
      @GadgetReboot  3 роки тому

      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

    • @Netlife-001
      @Netlife-001 3 роки тому

      @@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

  • @lordrahulcool
    @lordrahulcool 3 роки тому

    I hqve q circuit which needs 2n3819
    I cannot find 2n3819 so Can i exchage 2n3819 with 2n5457??

    • @GadgetReboot
      @GadgetReboot  3 роки тому

      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

    • @lordrahulcool
      @lordrahulcool 3 роки тому

      @@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

  • @torqueboymechanic
    @torqueboymechanic Рік тому

    Shout out idol

  • @Tronzoid
    @Tronzoid 3 місяці тому

    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.

    • @GadgetReboot
      @GadgetReboot  3 місяці тому

      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.

    • @Tronzoid
      @Tronzoid 3 місяці тому +1

      Thank you so much. I was losing my mind trying to figure out which was correct. @@GadgetReboot

  • @RobertLongM
    @RobertLongM 3 роки тому

    Not working for me 🤨
    Got a J201 & BC547
    Zero reading

  • @conceptualengineering8946
    @conceptualengineering8946 2 роки тому

    I'm still confused about source and drain terminals, how to recognize them properly with DMM?

    • @GadgetReboot
      @GadgetReboot  2 роки тому +1

      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.

    • @conceptualengineering8946
      @conceptualengineering8946 2 роки тому

      But how we can say that it's source or drain?

    • @GadgetReboot
      @GadgetReboot  2 роки тому +1

      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.

    • @conceptualengineering8946
      @conceptualengineering8946 2 роки тому +1

      Thanks a lot 👍👍

  • @Columbariusify
    @Columbariusify 2 роки тому

    Is jfet actually mosfet?

    • @GadgetReboot
      @GadgetReboot  2 роки тому +1

      they are different in enough ways to be considered unique more than interchangeable.

  • @BadRonald1
    @BadRonald1 2 роки тому

    At 0:38 Im lost after that.

  • @slavoslavik4353
    @slavoslavik4353 Рік тому

    nefunguje to! pre transistor npn 3399 , c114 , pnp A1345, bez testera to nezistis !

  • @robertbennett972
    @robertbennett972 Рік тому

    I observe you are blocking the video with your hand....while placing the leeds....

    • @GadgetReboot
      @GadgetReboot  Рік тому

      One day I aspire to have an elaborate multi camera setup and better video editing skills