Connect with us

Current sources

Discussion in 'Electronic Design' started by john, Jan 13, 2006.

Scroll to continue with content
  1. john

    john Guest

    Hello,
    Please look at the following data sheet of an instrumentation amplifier

    INA2133.


    http://focus.ti.com/lit/ds/symlink/ina2133.pdf


    I am using it as a constant current source ( figure 16, page 13 ). I
    made the following changes in the circuit


    1. I put a capcitor in series with the load for AC coupling reason.
    2. The power supply of the circuit is +/- 15 volts.


    I have a following questions about the circuit.


    1. For example, if the circuit is producing 100microA and the load
    resistance is 1mega ohm then the complaince voltage will be +/- 10
    volts or the voltage across the load will be +/- 10 volts. How can I
    keep the complaince voltage or voltage across the load equal to +/-
    0.7 volts with the current of 100microA without changing the power
    supply which is +/-15 volts?


    Please advice!
    Thanks
    John
     
  2. Rich Grise

    Rich Grise Guest

    .
    Well, what load resistance would develop 0.7V with 100 uA through it?

    What's the reactance of the cap at the frequency in question?

    Good Luck!
    Rich
     
  3. john

    john Guest

    Hi,

    I am using a iridium oxide material as a load. when voltage exceeds the
    +/- o.7voltage limit, the material breaks down. I need to protect the
    material.

    Thanks
    John
     
  4. john

    john Guest

    Hi.

    +/- 0.5 will be ok too! please advice

    Thanks
    John
     
  5. How close to 0.7V do you have to go? Would (say) 0.5V compliance be
    enough, or do you need 0.699V?


    Best regards,
    Spehro Pefhany
     
  6. Rich Grise

    Rich Grise Guest

    What, exactly, is the specification of the load? Are you sure that
    what you want to use on it is a "current source", when the load is
    so touchy about voltage?

    What is it you're trying to accomplish? Please give an overall overview,
    like, "I'm trying to do so-and-so with such-and-such a thing, and the
    thing looks like this..." that sort of thing. (redundancy unintended,
    apologies to the pedant contingent ;-).)

    Thanks!
    Rich
     
  7. Ian Stirling

    Ian Stirling Guest

    If 0.6V (about) would do, then a couple of standard diodes across it
    will work.
    For 0.7V, two shocketty(sp?) diodes in series may work.
    If the sole aim is protecting the device.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-