Hello,
I read the opa2690 datasheet, and try to understand the following two issues:
1). On page 19, the frequency calculated from equation (6) is about 46 MHz, using C(f)=8.6 pF and R(f)=402 ohms given by the numbers on that page of datasheet. However fig 46 on the same page gives a different -3dB frequency of 18MHz, even these two should be approximately identical. So wonder why ?
2). On page 21, section "optimizing resistor values", the datasheet says : "For a noninverting unity-gain follower application, the feedback connection should be made with a 25Ω resistor, not a direct short. This will isolate the inverting input capacitance from the output pin and improve the frequency response flatness. Usually, the feedback resistor value should be between 200Ω and 1.5kΩ." So wonder which one is correct, 25Ω or between 200Ω and 1.5kΩ ?
Thank you !
DL
