I am already using the AD627 that I find fantastic for example strain gauge measurement.

Now, my problem is to measure a current through a shunt of max 70 mV.

It is a PWM signal, thus, the information is a pulse where frequency is stable but the modulation is not. 

Therefore my output is also a pulse, what I can not use because I need a DC information, not a PWM one.

So, is there a special schematic / add/ filtering / else that I have forgotten ? 

In summary, I have a shunt before the load that works in PWM mode. I want to measure the current and get a DC voltage. Possible  with the AD 627 ?

Thanks for your help



IN+ voltage versus GroundIN+ : IN- differential voltage on shunt

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  • Hello 

    Thanks to both of you for your guidances. I will try it and hope that I will be a good Kirik, the first image is the voltage from IN+1/Ground.The second image is the IN+/IN- image with IN1 is the ground. The voltage is taken from a shunt of 70mV/200A just before the load. 

    You are great, I appreciate your help both of you.

    Will keep you informed.

    Regards to all


  • Hello

    I have succeeded to make it working with a RC filter after the output of the AD627. This one is a real exceptional amplifier. Thanks to everybody for the idea about the RC.

    Now, my friend, make me a favor and tell me if you know a AD627 that could have an input in a range of 0-30V. I work on a automotive application and as you know, alternators could go up to 28V-30V depending on the truck.

    AD627 is for a current sens PWM 1KHz measuring 100A - 35 mV.

    So, any idea for a "AD627" like for a voltage inputs in a range of 28V-30V ? I tried to find it on the website, nada..

     I have tried to put the sense shunt down, but at 35 mV, it is a soup, noisy and the RC is not effective at all. 

    Regards and merci beaucoup !!


  • Hi Vincent,

    As far as I understand, you use shunt in positive supply rail and you need INA which can work at 30 V common-mode voltage. But what can you say about the level-shift circuit?

    Zeners has low differential resistance and will not cause attenuation. You can use any 3 pin voltage regulator as a current source. But I have no idea if it will work in reality. What can you say about this?



  • Hello Kiril

    Thanks for your answer. With 2 zeners, I have tolerances of it to manage and it is a gap between of those entries of several mili volts so .... I have found a AD626, not so clear if it will work at those voltages but I will check. Have a nice day. Vincent