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OPA209: Bandwidth at 0db and 20db

GUOOO
Prodigy 140 points
Part Number: OPA209

In the video: https://training.ti.com/ti-precision-labs-op-amps-bandwidth-4?cu=14685 (TI PRECISION LAB -> OPA->5.4 TI Precision Labs - Op Amps: Bandwidth 4)

At 03:12 of this video, he said that 0db equals to 18MHZ, and 20db equals to 23.7 db, but the picture may not be. Actually, the 20db equals to 1.9MHZ, so what is your view?

THANKS!

  • 0
    Guru 48395 points

    Well, not to specifically look into those video's,this is kind of a topic de jure for some other things I am doing, 

    The attached steps through some sims with the V11 OPA209 library model. And the sim file below that - I could not find a model in the product folder?? 

    And then the gain of 1 closed loop sim showing about 23Mhz F-3dB. 

    OPA209 BW investigation using 2011 TINA model in the V11 library.docx

    This is V9 file, 

    Gain of 1 OPA209.TSC

  • 0
    TI__Guru* 93105 points

    Hello user5815340,

    I listened to the portion of the GBW discussion from time zero to a little beyond the 03:12 point and didn't detect an error. Right around the 03:12 time point the narrator is explaining that when the additional pole and zero occur in the open-loop gain (Aol) curve, following it to the point where it crosses 0 dB the gain-bandwidth frequency is 18 MHz. However, if the Aol curve is followed back to the point before the pole-zero occurrences where the Aol is about 10 V/V (20 dB), and then extrapolated in a straight line manner the gain curve would cross 0 dB on the X axis at 23.7 MHz. Thus, the GBW is different for the two Aol gain points being discussed.

    I hope this explanation helps.

    Regards, Thomas

    Precision Amplifiers Applications Engineering