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OPA2209: Setup opam

Lai Hai
Intellectual 685 points
Part Number: OPA2209

Hello everyone,

I really want to know what capacitor c11 has.

Reference:  http://www.ti.com/lit/df/tidr288/tidr288.pdf

  • 0
    Guru 48395 points

    Hello Lai, 

    THat is an AC coupling cap.At DC, this circuit has a gain of 1, but as the cap shorts out it rises to 32. The high pass pole is at 0.16Hz. When simulating, be sure to include the self resonance L of that cap as it will eventually give a LP pole as well as its inductance takes over. 

  • 0 in reply to Michael Steffes
    Intellectual 685 points

    Michael Steffes said:

    Hello Lai, 

    THat is an AC coupling cap.At DC, this circuit has a gain of 1, but as the cap shorts out it rises to 32. The high pass pole is at 0.16Hz. When simulating, be sure to include the self resonance L of that cap as it will eventually give a LP pole as well as its inductance takes over. 

    C11 and R9 will form a low pass filter circuit

  • 0
    TI__Guru* 93105 points

    Hi Lai,

    Michael provided a very complete explanation. Actually, C11 and R9 provide the high-pass response and provide a pole that breaks at 0.16 Hz. The ac gain is down -3 dB from the maximum 30.1 dB had in the passband. You can see this from the simulation shown below.

    Do you need anymore assistance with this circuit? If not, please go ahead and close this e2e inquiry.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Thomas Kuehl
    Intellectual 685 points

    Thomas Kuehl said:

    Hi Lai,

    Michael provided a very complete explanation. Actually, C11 and R9 provide the high-pass response and provide a pole that breaks at 0.16 Hz. The ac gain is down -3 dB from the maximum 30.1 dB had in the passband. You can see this from the simulation shown below.

    Do you need anymore assistance with this circuit? If not, please go ahead and close this e2e inquiry.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

    Can you tell me what the simulation is?

    Thanks.

    Hai Lai