Dc output

Discussion in 'Homework Help' started by frisbee4all, Feb 22, 2009.

  1. frisbee4all

    Thread Starter Member

    Feb 22, 2009
    13
    0
    Hey guys,

    I'm reading this book on Microelectrics and on of the examples they have is if you have a peak voltage of 10V and R = 1k-ohm, this would be for an AC supply voltage and circuit with a diode in it, find the peak value of the current in the diode and the dc component of the output voltage. I understand how to get the current ( V= IR), but not how to get the DC voltage output. The book just lists the value at 3.18 V, and the current at 10mA. any help would be great. Thanks
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Can you post up the circuit?
     
  3. frisbee4all

    Thread Starter Member

    Feb 22, 2009
    13
    0
    Not too sure how to do that. its a pretty simple circuit with a voltage source on the left, two wires one going up the other down. the top wire has a diode in it and after that there is the positive output terminal. the bottom wire leads to the negative output terminal. And there is a resistor in parallel to the voltage source that is after the diode but before the output voltage. there is nothing connecting the two terminals of the output voltage
     
  4. frisbee4all

    Thread Starter Member

    Feb 22, 2009
    13
    0
    Something like this...
     
  5. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    This is a half way rectifier.

    The voltage across the resistor will be the source voltage minus the voltage drop across the diode.

    The DC output voltage equals:
    Vdc=Vm/pi

    where

    Vm is the peak voltage across the resistor
     
  6. frisbee4all

    Thread Starter Member

    Feb 22, 2009
    13
    0
    Thanks mik3, could you extrapolate on the origins of that equation, it doesnt quite make sense to me visually. And also, would you use the same equation for a full-wave rectifier? Thanks
     
  7. vvkannan

    Active Member

    Aug 9, 2008
    138
    11
    Hi frisbee4all,

    Assuming vm sinwt as the voltage across the resistor,the dc output is give by the average value of vm sinwt.
    the average value is given by integrating Vmsin wt within the limits 0 to pi and dividing this answer by 2 pi (time period).so you get vm/pi as mik3 said.
    If we use a fullwave rectifier then the time period become pi so we get 2vm/pi
     
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