Question about Cadence IC5

[duron999]

cadence calculator independent variable

How can I change the X-axis or Y-axis to (Voltage vs frequency)
or can I use the output voltage in schematic to be X-axis to plot
the result ?

Thankyou !

 

[Fom]

vout vs vin graph in cadence

In waveform window select "Axis" -> "X axis" menu. There is a "Plot vs" button at the bottom of pop-up X axis window. Usualy it set to "Independent variable" but clicking on the button you can change X axis to any plotted waveform.
BTW what kind of analysis you are talking about? For AC analysis Voltage vs frequency is a default setting.

 

[duron999]

cadence vsin magnitude amplitude

In waveform window select "Axis" -> "X axis" menu. There is a "Plot vs" button at the bottom of pop-up X axis window. Usualy it set to "Independent variable" but clicking on the button you can change X axis to any plotted waveform.
BTW what kind of analysis you are talking about? For AC analysis Voltage vs frequency is a default setting.

oh ~ ic ~ i use traisent analysis to plot so i can't use it ! thanks !
Are there any tutorial teach these setting ? thanks !

 

[Fom]

Did you sweep frequency during transient analysis? How do you do that? Using FM source? Because if you don't sweep frequency your frequency is fixed. So to set the X axis as frequency is meaningless. It will be only one point.
If you explain what do you really want may be I can give you an advice.

 

[duron999]

Did you sweep frequency during transient analysis? How do you do that? Using FM source? Because if you don't sweep frequency your frequency is fixed. So to set the X axis as frequency is meaningless. It will be only one point.
If you explain what do you really want may be I can give you an advice.

I'm doing a CMOS op-amp design and i want to simulate the output like this
picture, however, my setting are wrong.... so the output shown nothing....
please help ! thanks !

 

[duron999]

Another question is, how can sweep frequency during transient analysis?
I can't find this option, thanks !

 

[Fom]

First, your picture is typical AC analysis. Why you run transient?
Second, your picture is taken not from Cadence IC5.
Third, you can get transient sweeping frequency by FM (frequency modulated) source, but your task is a simple AC analysis.

 

[duron999]

First, your picture is typical AC analysis. Why you run transient?
Second, your picture is taken not from Cadence IC5.
Third, you can get transient sweeping frequency by FM (frequency modulated) source, but your task is a simple AC analysis.

i'm going to do a DC GAIN analysis, circuit as shown below,
however how can i set the setting to get a (Vout / Vin) -3dB curve ???
thanks !

 

[Fom]

however how can i set the setting to get a (Vout / Vin) -3dB curve ???

You can use "bandwidth" calculator function. It will return frequency when GAIN is 3db (or any other threshold) lower than DC gain.

 

[duron999]

however how can i set the setting to get a (Vout / Vin) -3dB curve ???

You can use "bandwidth" calculator function. It will return frequency when GAIN is 3db (or any other threshold) lower than DC gain.

can i use that to plot out below graph ?
and where can i find "bandwidth" calculator ?
thanks !

 

[Fom]

"Bandwidth" is a Special function of Cadence Analog Artist Calculator tool.
As I mentioned above it returns a single value, so you cannot use that to plot graph like in your attachment. But it can be useful when you want to see how is bandwidth varied when you change some design parameters. For example you can run parametric analysis with different current for OPamp and to plot graph where Y axis will be bandwidth and X axis will be parameter value (current for example).
If you want to plot graph like attachment just plot dB(Vout/Vin).

 

[duron999]

"Bandwidth" is a Special function of Cadence Analog Artist Calculator tool.
As I mentioned above it returns a single value, so you cannot use that to plot graph like in your attachment. But it can be useful when you want to see how is bandwidth varied when you change some design parameters. For example you can run parametric analysis with different current for OPamp and to plot graph where Y axis will be bandwidth and X axis will be parameter value (current for example).
If you want to plot graph like attachment just plot dB(Vout/Vin).

Thanks !!! Let me try it tomorrow at school !

 

[duron999]

If you want to plot graph like attachment just plot dB(Vout/Vin).

Hello, Fom, I try it today, however.....
it can't work, the graph and my setting shown below,
what is the problem of my setting ??? How can i plot the true DC gain graph??? thanks !

 

[Fom]

You put Vsin as V0. Set TRANSIENT amplitude = 1V and sweep TRANSIENT frequency. Both of them are not valid for AC analysis. AC analysis use DC voltage of this source to calculate operation point, AC magnitude and phase to define where is source of your variable.
You should set AC magnitude = 1m (Frankly speaking you can set this magnitude to any value. It has almost no effect on result), VDC=0
Sweep variable should be set as FREQUENCY.
Set Frequency range as you want and run simulation.
Good luck.
Fom

 

[duron999]

You put Vsin as V0. Set TRANSIENT amplitude = 1V and sweep TRANSIENT frequency. Both of them are not valid for AC analysis. AC analysis use DC voltage of this source to calculate operation point, AC magnitude and phase to define where is source of your variable.
You should set AC magnitude = 1m (Frankly speaking you can set this magnitude to any value. It has almost no effect on result), VDC=0
Sweep variable should be set as FREQUENCY.
Set Frequency range as you want and run simulation.
Good luck.
Fom

sorry Fom, i have set the setting below, but the result is the same as before.......

I want to plot Vout over Vin as Y-axis and Frequency as X-axis,
i think i my graph only plot Vout, but how can i plot Vout over Vin ???
Thanks !

 

[Fom]

What do you mean Vout over Vin? Is it Vout/Vin or Vout - Vin?
And what does that mean the same result? If result is absolutely the same plot so the following reason can cause that.
1. You didn't apply any AC magnitude to input source.
2. Your schematic under OP AMP symbol doesn't work.
You can try a simple RC network to make sure that all your simulation procedure is OK.

 

[duron999]

What do you mean Vout over Vin? Is it Vout/Vin or Vout - Vin?
And what does that mean the same result? If result is absolutely the same plot so the following reason can cause that.
1. You didn't apply any AC magnitude to input source.
2. Your schematic under OP AMP symbol doesn't work.
You can try a simple RC network to make sure that all your simulation procedure is OK.

Vout over Vin is mean Vout divide Vin <= DC Gain

Yes... the result are the same as before...
so... let me check it again tomorrow, thanks !