Pnp & Npn

Discussion in 'General Electronics Chat' started by magdyfayad, Aug 20, 2007.

  1. magdyfayad

    Thread Starter New Member

    Aug 20, 2007
    this is a first thread for me

    I attached a file and contain one question , if posible answer it and explain in details the differencd between comon emitter ( transistor is good as a switch ) and common collector ( transistor not good as a switch ) and why transistor not good as a switch at common collector ??

    you can look to the file attachement and describle please in details what are the differences betwenn Q1 , Q2 and between Q3 ,Q4 as i know Q3 , Q4 is not good as a switch , why ??

    so i want to know what the voltage applied between the emitter and PLC input for Q3 ,Q4 in both cases Q3 , Q4 are on and are off