The problem of the pressure controlled constant current source made by op-amp

Discussion in 'Digital Circuit Design' started by zaizhetian, Sep 11, 2017.

  1. zaizhetian

    Thread Starter New Member

    Aug 30, 2017
    6
    0
    Hello,
    The following diagram is a simple constant current source that I used OP07 constitute to make. The first op-amp is to isolate the influence of the input to the constant current source.

    [​IMG]

    But I found that when the load resistance is connected, no matter how the input voltage, voltage of the J4 didn't change. And when change the load resistance, the voltage of the J4 changed, but can not meet the effect of constant current source.
    Why this happened? Is there a better circuit or chip to make a constant current source?
    Help,please~
     
  2. crutschow

    Expert

    Mar 14, 2008
    19,523
    5,444
    A constant-current source requires a load to ground.
    I don't see one in your schematic.
     
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