I am simulating a Fully Differential Opamp with Switched Capacitor CMFB.
I have a specified input frequency, say 30MHz for the sinewave input.
I am sampling at 100 MHz. I want 1024 samples.
I want to find the SNR of this structure based on the sizing of the transmission gates used for the switches.
My question: how to do I calculate the FFT of the output waveform ?
I dont want windowing the discrete-time output signal and want to make sure that the output samples have complete samples.
So based on my example, I pick 30MHz/100MHz * 1024 samples = 307.2. I choose the closest prime number -> Say, 311.
Then, the input frequency I put into the amplifier will be 311/1024 * 100 MHz = 30.37109375 MHz.
Then I just extract the data using value function in cadence, making sure I wait until the SC CMFB settles and then I output this to matlab and plot.
I use PRETTYFFT (not sure if you've heard of it):http://www.utdallas.edu/~yxc101000/courses/7327/proj/prettyFFT.m
Is this methodology correct for doing this in Spectre ?
Thank you for any advice or tips.