Hi hpham,
I suppose I am going to face the same problem as you as  I am designing the same circuit.
At the moment I still wonder which simulator between spectre and eldo is the best to do this.
I read " simulating switched capacitor filters with spectre RF"  and also "device noise simulation of sigma delta modulator".
The spectre way of doing the simulation is not completly clear to me .
Did you try to do the simulation with eldo and its noisetran analysis?
I think I am going to test spectre RF on an ideal amplifier using ideal switch and ideal capacitor in order to check what is the output noise.
have a nice day
 horizon

Sheldon,
Thanks for your reply. I though I set maxac freq big enough ( = 100M). More information about my setup : input freq = 12.5K, sampling clock = 200KHz, Bandwidth = 100KHz, amplifier's voltage gain = 72dB ( 3 stages in cascade, each = 24dB) . Input capacitor = 64pF, feedback capacitor = 4pF. When using maxsideband = 20, output noise density = 50.7nV2/Hz. msb = 50 , output noise = 87.7nV2/Hz. That's for the case of one single time point. I am thinking about choosing 2 time points to represent the peaks of output voltage, but i don't know how.
Horizon,
Thanks for your reply. I don't have access to Eldo.
best regards,
ha

Ha,

 I don't understand your comments about selecting two points
at the peaks of the output voltage. Does your testbench have
an input signal? Shouldn't the input be grounded when simulating
noise?

  It is easier for me to think about this in terms of S/H behavior so
I will describe the behavior that way. My understanding is that
you need to evaluate two conditions:
a) the sampling mode noise, measured at the instant the sampling
   when the S/H switches to hold mode
b) the hold mode noise, measured at the time when the next
   stage samples the output

For a S/H operating at 10MHz and a 50% duty cycle, I would
select two time points,  50ns and 99ns.

For a test circuit I built, the sample noise 1.25mVrms and the hold
noise was 3.45mVrms so the total is 3.67mVrms from PNOISE. In
my case the op-amp and sampling circuit are wideband so I needed
to use a lot of sidebands, ~100.

                                                        Hope this helps,

                                                           Sheldon

Hi guys,
I am also designing some switched capacitor filters and facing the same problem...i am following Ken's tutorial on SC filter simulation in Spectre RF...For time domain noise analysis what i do is,i make input dc voltage source zero and then no input source is selected ,noise type is selected as time domain....but it does'nt work at all???
also i am confused abt stop freq??