Calculate PSRR of bandgap voltege reference by hspice

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paramis

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hi
could anyone tell me how calculate PSRR of the voltage reference in dB at ac analyse by hspice?



i want to get this result by hspice ?
 
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To do that, can you show expression to calculate Vref?
 

paramis said:
... how calculate PSRR of the voltage reference in dB at ac analyse by hspice?
Click to expand...

Insert a sine wave interference source of - say - vis=100mV in series with your VDD supply and run an ac analysis. Then display vref/vis in dB units (vref is the ac part of vis passing through to the node Vref).
 

excuse me
can u write the command? i do not understand your means?
I use this command in hspice:
vdd vdd 0 dc=1.5 ac=1
.ac dec 10 1 20x
.probe ac vdb(vref)

but i cant get that result.
 

I think you miss
Code: 
.OPTION POST
see here: View attachment OPTION_POST_p368_412.pdf

Depending on your wave tool, may be for plotting you need
Code: 
[B].plot[/B] ac vdb(vref)

To get the same frequency range as in your above shown plot, you'd change the .ac command to
Code: 
.ac dec 100 100 10x
 

tnx alot
i get this result and it is not same fig4.(it is my problem)
 

You'd better use also a logarithmic presentation of the frequency (x-axis).
 
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