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    Designing a variable current source

    Hey!
    I want to design a variable current source, voltage controlled - from 0.1mA to 2.5A.
    Do you have any tips, circuits, etc?

    Many thanks!

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    Re: Designing a variable current source

    There are dedicated IC's that do this ...

    https://www.analog.com/en/design-cen...nt-source.html



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    Re: Designing a variable current source

    What voltage, high side or low side? A diagram of exactly what you want would help.

    Just google 'current source' and you'll see many topologies.



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    Re: Designing a variable current source

    Hi,

    this already has been discussed many times.
    You will find many threads here in the forum and many more in the internet.
    Simplest: click on the links in the box below "similar threads".

    Btw: I agree with the posts above. Missing a lot of your requirements / specifications.

    Klaus
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    Re: Designing a variable current source

    Also is there a frequency response requirement for the current source?
    Zapper
    Curmudgeon Elektroniker



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    Re: Designing a variable current source

    Hey all!
    Thanks for replying.
    I'm currently working on specification.
    All I know for now is that the control voltage should be 0-5V OR 0-10V, preferably to 0-5V.
    About a block diagram- attached
    Click image for larger version. 

Name:	Capture.JPG 
Views:	4 
Size:	28.0 KB 
ID:	153211

    Klaus, What does it mean high side or low side?

    Thanks again. I will try and go through similar posts and come back if I'll have any more questions:)



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    Re: Designing a variable current source

    Hi,

    What does it mean high side or low side?
    High side current source: Transitor at VCC (high side), load at GND
    Low side current source (current sink): Transistor at GND (low side), load at VCC

    Klaus

    - - - Updated - - -

    Added:

    Because this question comes so often, I even made some kind of tutorial here in this forum:
    https://www.edaboard.com/showthread....current-source

    Klaus
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    Re: Designing a variable current source

    Hi,
    Thanks for clarifying.
    I looked on your tutorial and tried simulating it at LTSPICE and didn't get any results.
    I'm still reading about it in various sources.
    The things I see the most are an OPAMP in which the output is connected to a transistor (BJT or MOS) that opens the current for the load.
    How do I begin in designing a one of my own? How do I chose the opamp, the type of transistor, etc?


    The requirements I have so far:
    - Controlled current- between 0.1mA to 2.5A
    - Controlling voltage- 0-5V
    - No frequency response as far as I know
    - About high/low side- I will read about it more in order to figure out what is best for the design.

    Thanks again.



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    Re: Designing a variable current source

    Post the LTspice circuit you tried to simulate.
    Zapper
    Curmudgeon Elektroniker



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    Re: Designing a variable current source

    Hi,

    How do I begin in designing a one of my own? How do I chose the opamp, the type of transistor, etc?
    There is a tutorial.. and you ask how to start.
    ...Maybe start telling us what you did so far and what results you get. Informations like "didn't get any results" arenīt helpful..

    How do I chose the opamp, the type of transistor, etc?
    OPAMP:
    Uncritical. Use a common one for the simulation. If the simulation fails it wonīt burn down your house. Thatīs the benefit of a simulation.
    For real world: Power supply should meet your requirements... Thatīs the most critical.

    Transistor:
    .... is written in the tutorial.

    Klaus
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    Re: Designing a variable current source

    Here's a common, low-side, constant-current circuit consisting of an N-MOSFET and an opamp.
    The op amp must be a single-supply type, and the MOSFET should be rated for at least 5A.
    The MOSFET must be mounted on a heatsink.
    R1 should be a 1W resistor.
    The circuit values shown give a current of 0-2.5A for a 0-5V input.
    Zapper
    Curmudgeon Elektroniker



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    Re: Designing a variable current source

    Hey
    Here is the simulation I ran:
    Click image for larger version. 

Name:	CurrentSourceSimulation.JPG 
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ID:	153246

    The graph is the Iload vs V1 (Input)

    I think the problem is with the transistor and OPAMP I chose? I will try to simulate again. Thanks!

    31crutschow, Thanks. I will try it as well.



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    Re: Designing a variable current source

    Hi,

    you missed to add the 40k resistor between R5 and R6..

    Klaus
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    Re: Designing a variable current source

    The opamp in your circuit should be a rail-rail (RR) type.
    Zapper
    Curmudgeon Elektroniker



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    Re: Designing a variable current source

    Hey everyone
    For the meantime we decided to try the solution summitville offered, a dedicated IC: LT3083 & LT3086.
    I will update in any changes or progress I will make in them or in the other circuits.
    Thanks for the help!



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