Simple Switching Circuit

Discussion in 'General Electronics Chat' started by Abdel_Rahman, Aug 3, 2016.

  1. Abdel_Rahman

    Thread Starter Member

    Jul 19, 2016
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    I have that model for a circuit used for IGBTs firing

    I want to energize A then B from microcontroller in a frequency about 50kHZ. with about 10 mA
    I want microcontroller pin not to be loaded with more than 1 mA.
    firstly I have intended to use "transistor as a switch" but I can not use it with common collector because the ground is common, so I have use it as common emmtier. but the problem is the output current is not greater than 3mA even if using Vcc for transistor with 12V and higher current gain models (2n2222, bc247...)
    Also I can not use optocoupler as circuit frequency is high (about 50kHZ)
    I am searching for a solution. Thanks in advance
     
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  2. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Could you do it like this?
    AB-pulser.JPG
    What model and circuit? How are they related to the A,B switching?
     
  3. Abdel_Rahman

    Thread Starter Member

    Jul 19, 2016
    36
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    No I can't as A and B are common connected
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Try this then :-
    AB-pulser2.JPG
     
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  5. jsallas

    New Member

    May 17, 2016
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  6. Abdel_Rahman

    Thread Starter Member

    Jul 19, 2016
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    Thanks for all,

    But what if there is any problems with R1 and loose connection to Vcc, can there is any unexpected operation of PNP transistor??
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Yes. Any circuit you use can have problems under certain circumstances :rolleyes:
     
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  8. #12

    Expert

    Nov 30, 2010
    16,257
    6,757
    Lacking R1 will allow Q2 to be enabled more easily if there is any leakage through Q1.
    Lacking Vcc will stop Q2 from activating.
    If you have these problems, repair them.
    Anyone who posts a schematic expects you to assemble it correctly. If you leave parts badly connected, it is nobody's fault but your own.
     
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