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Can't identify if transistor is PNP or NPN?

Discussion in 'General Electronics Discussion' started by Hugh Notman, Apr 24, 2016.

  1. Hugh Notman

    Hugh Notman

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    Dec 5, 2015
    I'm kind of a newbie with electronics but I do know how to differentiate the two generally. But in this there aren't any of the common markers. If I had to guess it would be NPN but I can't be certain. If someone more experienced could help me out that would be great.

    Also, if there are any guitar pedal guys out there, does the pot control the overall fuzziness of the circuit?

    Thank you very much (all help is appreciated)
     

    Attached Files:

  2. dorke

    dorke

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    Jun 20, 2015
    What at terrible circuit diagram.o_O
    No need to guess,the Emitter-arrows point inwards ==> they are both PNPs.
    Here is a site that will clear things for you,
    and another one here.
     
    Last edited: Apr 25, 2016
    hevans1944 likes this.
  3. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    Here's the original 50 year old circuit

    [​IMG]
     
    Arouse1973 and hevans1944 like this.
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    Just like on a map, the arrow points to N.

    on the transistor symbol, if the arrow points out, it's an NPN transistor (because the N's are on the outside). If it points in, out must be PNP.

    on a mosfet or jfet the arrow also pointed to N. Pointing inward, it must be an N channel device, so pointing out means P channel.
     
    dorke likes this.
  5. Nicholas MacNaughtan

    Nicholas MacNaughtan

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    Apr 25, 2016
    Hi I am very new to electronics, I am using a BF195 transistor, and I am not sure which pins are the base, collector and emitter. I have looked for schematics' online but can't find any. I am pretty sure it is an N-P-N. Please help. Many thanks in advance. Regards Nick
     
  6. dorke

    dorke

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    Jun 20, 2015
    Excellent analogy,could you believe that's the first time I hear that.
    Learning something each day,I like it:)
     
    davenn likes this.
  7. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    .


    Sir Nicholas MacNaughtan . . . . . . .


    Had to dig thru ye olde design reference library for that one . . . .


    [​IMG]

    From the words uf der Katzenjammer Kids . . . . . .

    Ahhhhhh chesss ve dun just bin gettink in und fresh 'chipment dis mornink . . . . und vud you be wantink vit der left handed or der left handed vershuns?
    Und vud you be wantink schmidt der clockwise electron flow fer der norths uf der equator . . . ..or fer der counterclockwise electron flow fer der souths uf der equator ?



    73's de Edd



    .
     
  8. cjdelphi

    cjdelphi

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    Oct 26, 2011
    I made a rule...

    npn (n)ot (p)ointing i(n)
    Pnp (p)ointing i(n)
     
  9. Nicholas MacNaughtan

    Nicholas MacNaughtan

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    Apr 25, 2016
    that's great thank you is that looking at it from the flat side of the transistor, many thanks,
    Nick
     
  10. duke37

    duke37

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    Jan 9, 2011
    The connections of various transistor differ. Sometimes the collector is in the middle, sometimes at the end. You will need to look up the data or measure the transistor for gain.
    Note that just to confuse, some transistors of one type have a different connection layout, these may be labelled with an L after the number.
     
  11. 73's de Edd

    73's de Edd

    2,728
    1,116
    Aug 21, 2015
    .



    Sir Nicholas MacNaughtan . . . . . . .

    In this manufacturers cases point of reference, it is being the 45 degree slope, that's notching off of the whole top corner, above the collector side of the transistor.

    73's de Edd



    .
     
  12. mark krawczuk

    mark krawczuk

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    Dec 17, 2015

    hi, get one of these, this will i.d the connections.:

    http://www.ebay.com.au/itm/All-in-1...691216?hash=item51d8fb2f10:g:HV0AAOSwWnFWCm30
     
  13. elebish

    elebish

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    Aug 16, 2013
    Purchase a "PEAK" atlas DCA55 semiconductor tester from MCM Electronics. Inexpensive and will tell you everything you will need to know about transistors including lead ID and specs and whether the transistor is bad or not.
     
  14. Lionel44

    Lionel44

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    Jan 11, 2014

    A transistor has 3 leads and is basically two diodes back to back with the outer leads going to the EMITTER and the COLLECTOR and the middle lead going to where the junction is. which is the BASE. Not all transistors have the same lead configuration, although most times the BASE is the middle leg and the COLLECTOR is tied to the case. A simple multimeter switched to OHMS can tell you the polarity and lead configuration. Select 2 leads and put the multimeter across them, if you have selected a BASE/EMITTER diode, the multimeter will read low resistance one way, then reverse the leads and it will read high resistance. Repeat to find the BASE/COLLECTOR diode. If you have selected the EMITTER/COLLECTOR 2 outer legs the multimeter will read high resistance both ways. Check with a diode to check the polarity of your multimeter output. +ve on the ANODE will give a low resistance reading.

    The verse Pointing In (PNP) and Not Pointing In (NPN) is true.

    Also, the EMITTER is always connected to its polarity ie. PNP is always +ve. NPN is always -ve
    The COLLECTOR is always connected to its opposite polarity ie. PNP is always -ve and NPN is always +ve.
     
    duke37 likes this.
  15. Lionel44

    Lionel44

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    Jan 11, 2014
    Forgot to mention -
    The 2 diodes in a NPN transistor are pointing towards each other and in a PNP transistor the 2 diodes are pointing away from each other
     
    Mongrel Shark likes this.
  16. duke37

    duke37

    5,253
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    Jan 9, 2011
    On the resistance range, an analog meter usually puts a positive voltage on the black lead and negative on the red lead, this can confuse things.
    Do not use the lowest resistance range, this can blow delicate transistors.
    Just keep a known transistor to compare.

    If the transistors are being used in a circuit, then there will be about 0.2V for germanium and 0.6V for silicon between emitter and base.
    Some early transistor circuits used a positive 'earth' and all later ones use a negative 'earth'.

    I went to Buxton on the Transpeak bus to buy a Peak meter. Lovely ride.
     
  17. elebish

    elebish

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    Aug 16, 2013
    Very true but my method is much simpler, inexpensive and better for a novice. I have one and love it. I use it instead of my curve tracer unless I want to match one device to another.
     
  18. Lionel44

    Lionel44

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    Jan 11, 2014
    I can recall hiking thru' Dovedale in my youth.Thanks for stirring great memories.
     
  19. Mongrel Shark

    Mongrel Shark

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    Jun 6, 2012
    I have a dca55 and a couple of $15-$30 ebay component testers similar to this one
    http://m.ebay.com.au/itm/All-in-1-C...eter-Inductance-BoBo-/351532691216?nav=SEARCH


    I like the cheap ones better! Just as acurate. They also give capacitance readings on diodes and transistors. As well as test inductors and capacitors including esr.

    Having said that. I often still use the diode test on a multimeter to id npn or pnp or to find the base.
     
  20. bannerman

    bannerman

    1
    1
    Dec 9, 2011
    Many cheap basic multimeters have a transistor test function.
    Select the transistor test range, and try the device in the test socket various ways round.
    When the display shows the greatest amplification, that is the correct pinout.

    There a also many "Component Analysers" available which will give even more information on the component. (Very cheap from the Far East on places like Ebay,)

    Datasheets for transistors which give you all specifications.are free on the internet.
    Ideally get them from the manufacturer's website, or just search for "Datasheet [device code]", e.g. "Datasheet BF195"

    Most transistors and components are made by many different manufacturers.
    (Look up "second sourcing" on Wikipedia.) So even a datasheet from the wrong manufacturer will give the approximately correct information.

    Many electronics hobby sites have beginner's courses on electronics.
     
    Mongrel Shark likes this.
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