PNP transistor: E, C and Base

Discussion in 'General Electronics Chat' started by forumito, Jul 24, 2010.

  1. forumito

    forumito Thread Starter New Member

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    Hello to all,

    I'm having trouble finding out the "pinout" of a A933 PNP transistor.
    The manual says
    But (as far as I can see) A933 is flat on both sides!

    Here is the picture of A933: [​IMG]

    What do "S" and "R" stand for ... "Set" and "Reset" as in SR latch? And "J"? Should these tell me which pin is E, C and Base?

    Or is there some convention that, no matter the transistor type/model, "flat side" is the side with label on it?

    Thank you for helping a humble novice. :)
  2. tom66

    tom66 Senior Member

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    That's not a TO-92 case. It's a special type of flat TO-92. The numbering usually refers to left-to-right on the side which has the part number and assorted writing. I think the name is "SPT".

    It is not an SR latch, you would need at least 2 pins for power, 2 inputs and 1 (or 2) outputs, more than 3 pins.

    Here is the datasheet for that PNP. It's apparently the 2SA933, I guessed this and it seems to match. Datasheet is pretty poor quality but we can see that the pins are numbered emitter->collector->base. If you plug this into any multimeter with transistor test in this configuration, and it shows a valid Hfe (i.e. greater than about 30) then you know the pinout is correct. The datasheet suggests a Hfe of 120 to 560.

    http://pdf1.alldatasheet.com/datasheet-pdf/view/107606/ROHM/2SA933.html
    Last edited: Jul 24, 2010
  3. forumito

    forumito Thread Starter New Member

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    I was reading this datasheet just before posting: as there are no labels in the document ... how do you know that the side with the label is the "flat side"? :)
    Is it safe to assume that labeled side = "flat" side? That is, can PNP (or NPN) transistor get damaged if improperly connected (within reasonable current of course)?
    [​IMG]
    I've looked into multimeter manual and it says:
    "Transistor tests can only be performed with the optionally available measuring adapter." That implies I need an extra device?
    "No voltage may be applied and measured on the adapter." No voltage may or can't be applied? :confused:
  4. tom66

    tom66 Senior Member

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    Hmm, going and buy one of those really cheap Mastech meters for about £2.99 just for the transistor test seems like too much. One of my meters came with an external transistor tester, but your meter manufacturer may have been cheap and skimped on this. No voltage may be applied, that means if you do damage could occur to the meter.

    I mentioned that the labelled side is always the "flat side". It is also usually the longest side, note that the other side has probably got little triangular cuts in it...

    The low voltage/current a meter provides will generally do no harm to a transistor if connected backwards. The story is different if you are dealing with a circuit with higher voltages or currents, you can destroy transistors easily... it's usually quite spectacular, sparks n' smoke.
    forumito likes this.
  5. hgmjr

    hgmjr Moderator Staff Member

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    I believe if you look closely, you will notice a slight beveled edge. This is the key to establishing the orientation. I believe it is along the left side of the device shown in your picture.


    hgmjr
  6. beenthere

    beenthere AAC Fanatic!

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    Another way to locate the base - it will be the only pin to show a junction to the collector and the emitter both. You can find that with the resistance function (the PN junction function is better) on your meter.
  7. SgtWookie

    SgtWookie Expert

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    I read the markings to say:
    Code:
    A933
       _
    S.RJ
    I frequently use Beenthere's method to do a quick transistor check using the diode function.

    Depending on how fresh your meter's battery is, a reading of around 500 to 750 is OK.
    If it's under 200, that junction is likely shorted.
    If it's > 750 or so, it's probably open or intermittent.

    You'll only get readings from the base to the collector and emitter.
  8. forumito

    forumito Thread Starter New Member

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    Now, "flat" side is the one with more or less bevel? :)
    [​IMG]
    Thank you for handy multimeter suggestions.
  9. tom66

    tom66 Senior Member

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    The flat side as mentioned is the side with the labelling.

    Do a meter check to be certain.
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