OUTPUT impedance buffer

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

  1. unlv007

    Thread Starter Active Member

    Apr 5, 2008
    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
    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
    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
    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


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

    AAC Fanatic!

    Jun 18, 2008
    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


    Mar 24, 2008
    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.