Dear wgtkan, Thank you for your added comments - I just wanted to verify that the DC operating point was in the high gain region! [quote userid="289980" url="~/cadence_technology_forums/f/custom-ic-design/46633/cmrr-simulation-setup/1369033"]. The last plot seems correct but the earlier one was not right. [/quote] My interpretation of your last plot is that it represents the differential gain of your op-amp versus frequency while the former curve represents the CMRR versus frequency. Am I correct? A concern I have is that it appears you are simulating your op-amp in an open-loop configuration (i.e., without any feedback network). As a result, I am concerned that your CMRR and gain curves are not representative of what you are expecting. If you are intending to use this amplifier in a closed loop configuration, in addition to including the load, I might suggest including the feedback network and then simulating the differential gain and CMRR. I don't think the CMRR curve you generated is meaningful in an open loop configuration to easily extract the CMRR in any given closed loop configuration. If your interests are in the loop gain of your amplifier, I might suggest then adding the appropriate probes and use a stability analysis (differential) in its closed loop configuration rather than running an XF analysis in its open-loop configuration. Does this make sense wgtkan? Shawn
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