OUTPUT impedance buffer

Discussion in 'The Projects Forum' started by unlv007, Apr 5, 2008.

  1. unlv007

    Thread Starter Active Member

    Apr 5, 2008
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    I am trying to drive a high resistance load (5-10K) through a constant current source. But the current source is not very good and has a low output resistance, modeled as a shunt resistor and thus when i connect it to the high resistive load, much of the current flows through its own shunt resistance.Can i connect something in between the current source and the load so that loading effect is avoided.
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Why not just design a high resistance current source??
    Most of them are in the Megohms. 5-10k is nothing to them so the current is constant.
     
  3. unlv007

    Thread Starter Active Member

    Apr 5, 2008
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    Most current sources internal output resistances are usually in Megohms. If the voltage rating of my current source is less than what the load demands, what can i do to compensate? When i use a high quality current source (TO WHICH I HAVE LIMITED ACCCESS) i see that the load voltage rises from 0V to about 40V in a linear fashion for about 5 s and then remains constant at 40V under a const current of 40mA.GIVEn these parameters, does anybody know about a compensating circuit etc???
    thanks in advance.
     
  4. cumesoftware

    Senior Member

    Apr 27, 2007
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    I think if you get one with a higher voltage and a higher output resistance, you will have a better approximation on an ideal current source. Say about 200VDC with a very big series resistance.

    Probably your current source is a 40V PSU connected to a current mirror (that explains why the cap charges in a linear fashion). The use of a current mirror to control the current is not a bad ideal at all. I find it better than the simple resistor.
     
  5. zorbzz

    Member

    Jun 16, 2008
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    Post removed by moderator
     
    Last edited by a moderator: Aug 19, 2008
  6. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
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    Edit by moderator - quote removed.

    There does appear to be a common theme to unlv007 posts :rolleyes:.
     
    Last edited by a moderator: Aug 19, 2008
  7. Wendy

    Moderator

    Mar 24, 2008
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    Guys, I believe these comments are out of line. You don't like someone, you don't post. Read the rules.

    This site is higher class than that. Consider it a no flame zone.
     
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