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OPA345 Gain when used a Current sense amplifier

Shihab
Expert 1205 points
Other Parts Discussed in Thread: OPA345

Hi,

 

I am planning to use OPA345 as current sense amplifier. I am thinking of using it because of its common mode voltage: -0.3V to V+ + 0.3. this is ok for my application.

 I have seen in the data sheet that gain will be 3MHZ if Gain>=5. Can anyone tell me how much will be the available bandwidth if the gain is 20.

 

Regards,

Shihab.

  • 0
    TI__Guru* 93105 points

    Hi Shihab,

    Sorry for the slow response; much of our department has been traveling with work, or on vacation. The closed-loop bandwidth can be calculated from the unity-gain crossover frequency (or gain-bandwidth product parameter) and the noise gain. You mention a gain of 20, which I'll assume is a non-inverting gain of +20V/V. For the non-inverting configuration the gain is the same as the noise gain value. Here is how you calculate the bandwidth:

    fc = fu / Gn,  where fu is 3MHz for the OPA345 and Gn= 20V/V

    fc = 3MHz / 20V/V = 150kHz

    The gain will be down -3dB at 150kHz in this case.

    Regards, Thomas

    PA - Linear Applications Engineering