TLV9001: How to use for differential amplify application

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Replies: 3

Views: 55

Part Number: TLV9001

Hi Team:

Nowadays, we are try to measure the current of the LED based on a  sensor resistance and differential amplify circuit. The schematic is below. The Vcc for TLV9001 is 4V stable. R5=R7=18K, R6=R8=100K Rsense=1Ω.  When we use a power supply as 50mA current source for the Vdrive. The voltage between Rsense is 50mV, while Vdrive is close to 2.5V. But there is no Vout from the TLV9001.

We have measured the voltage of IN+: 2.26V, IN-:2.23V. But for Vout, there is only 10mV. And after I add 0.1uF both IN-, IN+, 10uF at VCC, Vdrive. there is no change.

May you help to find out why the circuit couldn't work. Is the circuit right? Or we may need to add some caps some where? Thanks for your kindly support~

Best Regards

Minqiu

Best Regards

Minqiu

3 Replies

  • Hello Minqiu

    I suspect the op amp was damaged or the Vout node is accidentally shorted to ground.

    Try to measure the resistance from VOUT to ground while the power is off.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Ron Michallick:

    Hi Ronald:

    Sorry for delay as I'm during the business travel.

    We have try it several times with new parts and carefully soldering. Is there any risk to bring this issue?

    Besides, may you share some advise to built this current sensor circuit better and cheap? Thank you! 

    Best Regards

    Minqiu

  • In reply to Minqiu Xie:

    Minqiu,

    The circuit is a standard basic differential amplifier so it should work if properly wired (connected). 

    Can you repeat the 50mA test and measure and report the voltage at every pin (measure at the pin). 

    Also provide the full part number. Some part number options have different pinouts.

     

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).