NPN/PNP circuit

Discussion in 'Homework Help' started by mas928s4, Aug 14, 2014.

  1. mas928s4

    Thread Starter New Member

    Aug 14, 2014
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    I have this transistor schematic that has me scratching my head. I was wondering if there is somebody out there that can explain it to me. I know the basics of how a PNP and NPN transistor works but this configuration to me looks like a glorified switch? Also is the circled "A" an ammeter? and shouldn't it be a motor?

    Thank you,
     
  2. shteii01

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    Feb 19, 2010
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  3. Jony130

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    Feb 17, 2009
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    This is really bad design circuit. PNP transistor will work in "Inverted/reversed" region.
    You should swap the emitter with collector.
    And "A" for Armature.
     
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  4. mas928s4

    Thread Starter New Member

    Aug 14, 2014
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    Thank you for the link shteii. In all my years in field service I never ran across this configuration. I appreciate your quick response to my question,

    Have a great day
     
  5. mas928s4

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    Aug 14, 2014
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    Hi Jony130,

    The wikilink explained the theory behind the design (H Bridge) pretty well as far as reversing the polarity of a motor which fits well with robotics. I agree the design isn't the greatest but is all I have to work with at the moment.
     
  6. studiot

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    Last edited: Aug 14, 2014
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  7. Jony130

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    Hey what can I say. Try goggle "reverse active region".
    And the "correct" diagram should look like this
    http://forum.allaboutcircuits.com/attachment.php?attachmentid=71746&stc=1&d=1408034727

    And here you have a idiot-proof h-bridge
    [​IMG]
     
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  8. mas928s4

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    Aug 14, 2014
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    I'm not being critical as a matter of fact I am most appreciative of everyones input on this. To me its all good and useful information.
     
  9. Jony130

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    Ok, no problem. Any more question about the circuit?
     
  10. mas928s4

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    Aug 14, 2014
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    I don't think so I think everything good.
     
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