Hi, it is my understanding that the general transient analysis in SPICE or SPECTRE does not take into consideration of the random device noise, such as the thermal noise, shot noise, flicker noise etc. Is this right? If it is, so this means that the SNR obtained from transient simulation for A/D converters is the nominal SNR with quantization noise and other deterministic noise only?

So, how do we take into consideration of random device noise for general circuits, like OpAmps or even timing delay of digital circuits ? If there are 100 transistors in the circuit, how can the random noise for each transistor be considered in the transient simulation? Thank you for your help.

Generally the small signal noise analyses (noise or pnoise) are preferred over transient noise. You would use noise for the opamp and pnoise for the logic circuit.

-Ken