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OPA828: Why output voltage amplitude will decrease if input signal's frequency >1KHz

Part Number: OPA828

Hi team,

My customer use OPA828 to design voltage follower but they find if input signal frequency increase then output voltage amplitude will decrease at same input voltage amplitude. below is their circuit, please help to check is there any problem here?  Thanks

  • Hi Paul,

    the high ohmic voltage divider at the input in combination with the input capacitance of OPA828 performs a low pass filter:


    Make the input voltage divider less high ohmic Relaxed


  • The decrease of the output voltage is caused by the low-pass filter formed by a large R2 resistor interacting with the input capacitance of OPA828 - see below.  

    Thus, the attenuation of the signal occurs in front of the op amp and has nothing to do with the bandwidth of the OPA828 - see below.