noise analysis in Cadence....

cadence noise analysis

I hav simulated a simple PMOS buffer op-amp in hspice which generated by 3.3V supply & te result i get as below :
gain =25dB
t.output noise=3.58m V/√Hz
equivalent inp. noise = 188.4u V/√Hz

*While i tried te same cct in Cadence(Spectre) n i get te same o/p noise
t. o/p noise =12.87u V²/Hz
equivalent i/p noise =189.725u V/√Hz
eq. o/p noise =3.588m V/√Hz
squared i/p noise=35.9 n V²/Hz
squared o/p noise =12.87u V²/Hz

* But te prb is i cant use te NF command in Direct Plot (Cadence ), can ny1 plz let me knw how 2 use NF application...
* Noise simulation can b done using AC analysis, but do nybody knws how 2 do it in Transient analysis...

nf in cadence

which parameter is used for model,while simulate the noise.

noise analysis in cadence

As far you are using the same transistor thr is no difference whethe you simulate with HSPICE or Spectre. Coming to the noise analysis for NF try to use the port in analogLib instead of the ac source. I tried it and found it working.

noise analysis cadence

pnanda65675 said:

I hav simulated a simple PMOS buffer op-amp in hspice which generated by 3.3V supply & te result i get as below :
gain =25dB
t.output noise=3.58m V/√Hz
equivalent inp. noise = 188.4u V/√Hz

*While i tried te same cct in Cadence(Spectre) n i get te same o/p noise
t. o/p noise =12.87u V²/Hz
equivalent i/p noise =189.725u V/√Hz
eq. o/p noise =3.588m V/√Hz
squared i/p noise=35.9 n V²/Hz
squared o/p noise =12.87u V²/Hz

* But te prb is i cant use te NF command in Direct Plot (Cadence ), can ny1 plz let me knw how 2 use NF application...
* Noise simulation can b done using AC analysis, but do nybody knws how 2 do it in Transient analysis...

Click to expand...

you need to understand what the NF is before you actually do the simulation... it all starts from SNR. if you are clear about that, you should know why you can't get NF in the direct plot

noise analysis spice

As said by gunturikishore, if you want to calculate the NF, you need to use a "port" instead of the standard "vsin". NF can simply be seen as the noise your circuit add to the noise from previous stages. Vsin source don't generate any noise, whereas with a port you must specify the resistance value, which will generate some noise.Then you should be able to plot the NF.
As for noise simulation itself, I think it's not possible in transient (maybe you could find more details in a Spice book). In my understanding, noise model are not random sources, but equivalent fixed current or voltage source, whose value are fixed by the circuit operating point, and also the frequency. So that's why you perform the AC analisys. Also noise is expressed as nv/√Hz and then integrated over the BW to get the rms. So you kind of need the AC sweep somewhere.
I hope it helps a little