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OPA4188: Is rightly to use it as below?

Jacking Jin
Expert 1145 points
Part Number: OPA4188
Other Parts Discussed in Thread: INA149, OPA4191, OPA4192, TINA-TI

Dears,

I want to sampling the BUS voltage, the total voltage is about 800V(DC). I have adjusted to about 50V  through precision resistance voltage divider, and then, use the OPA4188 to realize it. The simple circuit as below, the BU+-BU- is arrived about 50V.

So I want to seek advice from you. Is this have problem like design?  Thanks very much.

  • 0
    TI__Mastermind 25775 points

    Hello,

    Please understand that most of our engineers are out for the holidays. It is most likely that we won't address your question until early January 2017.

  • 0 in reply to Pete%20Semig
    Expert 1145 points

    Dears,

    Could you kindly help me to answer the problem? Thanks very much!

  • 0
    TI__Guru 60570 points

    Jacking,

    For this kind of application, please consider using INA149 - it can handle the input common-mode voltages up to 550V. 

    If you wish to implement a difference amplifier, you must reference the output to an independent voltage source - it may NOT be connected to the output as shown on your circuit diagram.  Also, since this kind of application requires large input resistors, you should not use chopper applifier like OPA4188 (due to commutation of IB current spikes) but instead use a precision linear op amp like OPA4191 or OPA4192  - see below.  You do not specify the supply voltage or differential signal thus circuit below may have to be adjusted to make sure that the Vcm does NOT exceed the Vcc voltage.

    I also attached below the TINA-TI circuit so you may use it for your simulations.

    Jin Differential Amp.TSC