ADC driver output resistance

Hi viktor_vojta ,

I will move this thread here (+) Q&A - ADC Drivers - EngineerZone (analog.com). Someone here should be able to assist you in your queries.

Regards,

JC

I opened your Spice-model and it seems to me, that the model of output resistance is 11 Ohm. Is it correct?

Hi,

Keep in mind that negative feedback reduces the output impedance greatly. Typically the closed loop output impedance is equal to the internal output impedance divided by the loop gain. So it probably won't affect the filter characteristics at frequencies where the open loop gain is high enough. 

Hi,

Seconding this answer, output impedance should be fairly low but it increases across frequency. Depending on your frequency of application, the impedance will be almost negligible especially on sub kHz level. May I know what your frequency of application is?

Regards,
Goz

Thank you for additional info. My freq. range is DC...40MHz, the wanted signal BW (or better to say pass-band) is DC...22MHz. I did simulation and subsequently measurement on the AD Eval Board. And the measurement more or less verified the answer given by ZoltanDTI. First I expected results with Rout = 11Ohm, but results were different and I need to correct the simulation using Rout = 0Ohm, then it is OK. 

Hi,

I believe that the questions have already been answered so I am closing this thread. Thank you!

Regards,

Mae