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  1. R

    Programmable negative constant current source

    Hi Steve, Thanks for your help. I will give this a go today and let you know of the outcome. I really appreciate you taking time out to help. Best regards, Rajinder
  2. R

    Programmable negative constant current source

    Hi, Thanks for your help so far. Do you have a sketch if the circuit? What I understand is, that I have my current set up I.e. inverting opamp gain of -1, non inverting input at 0V. DAC connected to inverting input, so what ever is at the DAC output is seen at the opamp output but negative...
  3. R

    Programmable negative constant current source

    Hi, My idea was to have the drain of the FET go 0V, gate driven by opamp and the source providing the negative voltage. Will this configuration work? The output is taken from drain (as I need a common 0V) and the source end which has the feedback resistor to the opamp inverting pin. I look...
  4. R

    Programmable negative constant current source

    Hi, I have done this. With an inverting gain of -1 using 2 x 10 M resistors. Non inverting tied to 0v, DAC fed to inverting input stage, I removed the FET band placed resistor across the opamp output wrt ground. This works fine. But is open loop with no feedback control. I was looking at some...
  5. R

    Programmable negative constant current source

    Hi Here is the schematics. The first one works but I can't get a common ground between the load and the unit that it needs to connect too. Hence the second circuit idea, which gives the common ground but I can't get the negative current output. Can I connect the n channel FET drain to 0v and...
  6. R

    Programmable negative constant current source

    Hi, I will upload a schematic in a few minutes. Thanks for your reply. I need to get this to work, do would appreciate any help. Best regards, Rajinder.
  7. R

    Programmable negative constant current source

    Hi, Yes this is what I am doing. But I need to get a negative current output. Hence the drain to 0V and the output of my source to the load. I will upload a schematic in a few minutes. Thanks. Rajinder.
  8. R

    Programmable negative constant current source

    Hi, I was wondering if someone could help. I am building a programmable negative constant current source. The idea is as follows: DAC controlled from a microcontroller fed into the non inverting input of an opamp. The opamp has split supplies +/-5V. The out put of the opamp drives the gare of a...
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