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    How to let current source has linear V-I and can supply enough current?

    Hi, all

    I have a question need your help. Thanks in advance. I want to design a current source(CS) with the below requirement in 180nM.
    1. Voltage control and current have the linear relationship.
    2. Current mirror can supply enough current. It means if I let MOS W/L low enough to let CS work in triode region, it can has linear V-I. But it's very difficult to supply enough current. So that I have to use many CS in parallel (maybe 10 in parallel)which occupies a lot of area. I don't like to use this way.
    3. Add a resistor in source node: source degenerator. I think it can make V-I more linear, but current will be lower, right?

    May I ask if there is other circuit structures or methods which can realize linear V-I and enough current at the same time?

    Regards

    •   Alt10th June 2018, 16:37

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    Re: How to let current source has linear V-I and can supply enough current?

    A simple transistor is a method that gives linear response. However it is resistive drop therefore it generates heat. You may decide that several devices in parallel is the easiest solution, and/or several pins acting as multiple heat sinks in contact with the pcb.

    Simulation showing that the load receives a proportional Ampere level, based on the volt level coming from the left.

    Click image for larger version. 

Name:	NPN 15mA to 5 Amperes controlled by 0-5V signal input.png 
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    •   Alt11th June 2018, 04:03

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    Re: How to let current source has linear V-I and can supply enough current?

    Hi,

    I assume this is ASIC development.


    In either case specifications like:
    * voltage(s)
    * current range
    * linearity
    are essential.

    Klaus
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    •   Alt11th June 2018, 06:43

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  4. #4
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    Re: How to let current source has linear V-I and can supply enough current?

    Can you use a Typical V to I Converter? That uses an OpAmp?
    Provided the loop gain is high, you will get excellent linearity.
    Click image for larger version. 

Name:	V2I Converter NMOS.png 
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    You can use PMOS as well. And even have it Supply Referred.

    N5
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