diode in parallel with resistor

Discussion in 'Homework Help' started by u-will-neva-no, Apr 26, 2011.

  1. u-will-neva-no

    Thread Starter Member

    Mar 22, 2011
    230
    2
    Hello, I have attached an image and am required to find the current through the diode (Id) and and the current flowing through the resistor (Ir).

    Im using KCL so I have Is -Ir - Id=0 (where Is is the current source)

    10mA -Ir -Id =0
    Ir + Id = 10mA

    I dont know where to go from here however...I want to use ohms law to obtain another equation but due to no voltage source Im not sure...
     
  2. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
    2,804
    832
    u-will-neva-no likes this.
  3. bluemarvin

    New Member

    Apr 19, 2011
    8
    2
    The diode sets the voltage across the resistor...the voltage across both must be equal. If for some reason, voltage across the R and D climbed higher, more current would flow through the diode thus dropping the voltage back to .7V. Therefore the current through the resistor must be .7V/200R =3.5mA. Since you are driving both the resistor path and the diode path with a 10 mA current source, the rest of the current must flow through the diode, therefore it's passing 10-3.5mA=6.5mA.
     
    u-will-neva-no likes this.
  4. u-will-neva-no

    Thread Starter Member

    Mar 22, 2011
    230
    2
    Thanks you two!
     
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