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the information of low frequency in closed-loop OPA188

Henry Cheng1
Prodigy 180 points
Other Parts Discussed in Thread: OPA177, OPA188

I found there is no low frequency information in closed-loop gain in OPA188 datasheet. Could you provide the information of low frequency in closed-loop gain like as OPA177? Thanks.

  • 0
    TI__Guru 68461 points

    Henry,

    Knowing that OPA188 Gain-Bandwidth Product is 2MHz and that AOL slope is -20dB/decade, you may calulate -3dB frequency for any close-loop gain, Gcl, using following equation: f(Gain) = 2MHz/Gcl; therefore,

    for G=10, f=2MHz/10=200kHz

    for G=100, f=2MHz/100=20kHz

    for G=1000, f=2MHz/1000=2kHz

    for G=10,000, f=2MHz/10,000=200Hz, etc.

     

    You may also simulate it using OPA188 macro-model available on TI website where Gcl=Vout/Vin - see below.

    I have done the simulations for you by changing the value of R1 resistor for different close-loop gains-see below.