Transistor without base resistor

Discussion in 'The Projects Forum' started by vivek20055, Dec 20, 2012.

  1. vivek20055

    Thread Starter Member

    Nov 4, 2012
    88
    0
    Hi,

    why base resistor is used for transistor. what happens if base resistor is not there for a transistor?



    Best regards,
    Vivek Alaparthi
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    If its a bipolar it will destroy the transistor if omitted, ifs its a fet it wont do any harm.
     
  3. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    Some bipolar transistor circuits (such as common bases and common collector, and those that drive the transistor with a high impedance, such as the collector of another transistor) do not need a series base resistor to limit base current, but would use a base resistor to reduce the Q of the base circuit so that it won't oscillate at radio frequencies. Another use, particularly if there is appreciable capacitance between the base and collector in a common emitter circuit would be to control the rate of change of the collector voltage. There are probably a few other reasons one would use a base resistor, but there are some.
     
  4. vivek20055

    Thread Starter Member

    Nov 4, 2012
    88
    0
    Hello guys,


    Thanks for your replies.

    In the following circuit with transistors,base resistance is not used. why?



    Best regards,
    Vivek Alaparthi
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,090
    3,027
    Is it possible that the two base signals are current-limited somewhere else? If not, it's just wrong and will burn up.
     
  6. tubeguy

    Well-Known Member

    Nov 3, 2012
    1,157
    197
    Agree with Wayneh. If you apply for instance the 3.3 v to the right TR with no current limiting.. POOF !
     
  7. DickCappels

    Moderator

    Aug 21, 2008
    2,647
    632
    Some transistors that have internal series base resistors so that they can be turned on and off with control voltages without an external resistor. Such resistors are unusual, but they are exist.
     
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