I am new to cadence virtuoso/spectre. I want to design an ADC for which I have written some components through verilog A containing their respective noise models implemented through white_noise and flicker_noise functions.
Now how to activate those sources in spectre simulation ? It's only active in small signal analysis as far as I know. However I want noise to be present along with the main signal so that I can measure SNR etc using calculator function.So which type of analysis to use: tran or noise ? and how (few lines of analysis statement will help)
Moreover, from cadence virtuoso manual I found that we can perform small signal analysis during transient analysis, by using below command:
Name tran stop=stop actimes=time acnames=name
However I got a syntax error of "ERROR (SPECTRE-16062): Output of circuit is not specified." on running below code snippet on a simple test circuit :
tran tran stop=4u write="spectre.ic" writefinal="spectre.fc" \
annotate=status maxiters=5 actimes=[2u] acnames=[noise1]
noise1 noise start=2u stop=2.1u
finalTimeOP info what=oppoint where=rawfile
I stuffed another "info what=oppoint" statement between 2nd and 3rd line, still same error. Here my understanding is tran analysis stops at 2u and till 2.1 the simulator will run noise analysis (if wrong please correct me). I am still trying to debug this and it may be a plain syntax error. However can someone please answer above questions and guide me through the right approach.
Thanks a lot!
Thank you Andrew for elaborate replies!
To clarify your query on what I wish to model : is noise contribution from thermal /flicker noise of MOSFETs used in designing the adc circuit.I have created models for them in verilog A, So will u not recommend small signal noise analysis for this kind of problem ?
Apart from these sources and quantization noise and mismatches in design, I think a properly designed ADC will not have any other significant noise source. Am I right in assuming this ?
If I model these sources through transient noise and if I specify both fmin and fmax then I guess contributions from both of thermal and flicker noise fucnctions will be included in the output. Then I can take a DFT of time domain output.Another doubt is: do we use the spectral domain output of small signal noise analysis to calculate any noise figures ? or they are just there for information ?
Thanks a lot again !