Hi,

i would compare the noise performance resulting from transient noise (spectre) and pnoise (spectreRF) of a switched cap. circuit (i.e. an integrator).

Despite the exhaustive informations provided in "Simulating switched-capacitors filters with SpectreRF" (

http://www.designers-guide.org/Analysis/sc-filters.pdf), some clarifications are needed.

1) the maximum noise freq. ("noisefmax") in transient noise represents the stop frequency in pnoise analysis?

2) is the minimum noise freq. ("noisefmin") in transient noise related to the transient simulation stop time?

Assuming tstop the transient stop time the minimum frequency that can be observed is 1/tstop hence none noise contributions below this limit can be observed. Is this consideration correct?

3) Assuming the minimum noise frequency in transient noise analysis to be fmin. Does fmin set the start frequency in pnoise analysis?

Simulating a simple ideal sample and hold sampling at fck the expected noise power is kT/C where C represents the holding capacitance.

What's the difference between pnoise with "source" noise type and pnoise with "timedomain" noise type?

In order to match the kT/C expected noise power, the output PSD resulting from "source" noise type must be integrated over a wide bandwidth (integration bandwidth >> fck). Otherwise, in order to obtain kT/C, the PSD resulting from "timedomain" noise type must be integrated starting from fstart to fck/2 (and the accuracy depends on the number of sidebands considered).

Is this correct? Is this the right interpretation of the spectre and spectreRF results?

Many thanks, Matteo