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Variable Gain INA148

Sebastian Chinchilla
Prodigy 20 points
Other Parts Discussed in Thread: INA148, INA146, OPA188, INA149

Hi, I was wondering if there is a differential amplifier such as the INA148 but with a variable gain and a common-mode voltage of +-200V.

INA146 has a variable gain, but unfortunately its common mode is just +-100V.

Is it possible to modify the INA146 so that  its common-mode voltage is increased?, or is it possible to add another operational amplifier at the output of the INA148 to make it have a variable gain?

 

  • 0
    TI__Mastermind 25865 points

    Hello Sebastian,

    The INA146 is composed of a difference amplifier (A1) and an output amplifier (A2), which provides the gain. The gain of the difference amplifier is 0.1V/V due to the ratio R2/R1. The overall gain of the device is determined by Rg2 and Rg1.

    You can certainly cascade a difference amplifier with a stand-alone op amp to obtain the same functionality of the INA146.

    My recommendation, however, is to use the INA149 instead of the INA148 for your difference amplifier. This is because the INA149 has better CMRR performance. For the gain amplifier I suggest evaluating the OPA188.

  • 0 in reply to Pete%20Semig
    Prodigy 20 points

    Pete Semig said:

    Hello Sebastian,

    The INA146 is composed of a difference amplifier (A1) and an output amplifier (A2), which provides the gain. The gain of the difference amplifier is 0.1V/V due to the ratio R2/R1. The overall gain of the device is determined by Rg2 and Rg1.

    You can certainly cascade a difference amplifier with a stand-alone op amp to obtain the same functionality of the INA146.

    My recommendation, however, is to use the INA149 instead of the INA148 for your difference amplifier. This is because the INA149 has better CMRR performance. For the gain amplifier I suggest evaluating the OPA188.

    Hi Pete,

    Thanks for answering, your reply has been really useful. I just have one question: Cascading the op amp would affect the high common-mode voltage range of the INA148 or INA149?

    Besides, I think I will still use the INA148 because it can be used also as single supplied. I need to be able to handle 170 V as common-mode input, but sometimes just 13V max depending on the load ( it is for an adjustable  motor controller of different motor sizes ).

    Best Regards.