How to simulate the dc open loop gain v.s output range

[yschuang]

Hi, all

I was wonderign how to plot the dc open loop gain versus output range by using Hspice. Please see the figure shown here or go to
**broken link removed**
Thanks for your reply.

 

[MSSN]

Here is a nice trick to do so,
1-Put your amplifier in a unity gain feedback with a dc source at the input of the unit gain amplifier(the input of the feedback network).
2-Put another ac source at the input of the amplifier itself.
3-Vary the DC source across the output range and plot the ac voltage at the output of the amplifier which is simply the gain of the amplifier(assuming that the input ac source = 1V).

Note:This method assumes that the amplifier has high gain in order to have almost unity gain in feedback

 

[wonbef]

you can use sweep analysis and calculator to aid to plot it!

 

[boooser]

Use a balun for the input and output.
Vinp=Vid/2+Vic
Vinn=-Vid/2+Vic
Then give Vdm a dc sweep
plot the voltage of output node.
Use calculator to derive the output node. dVout/dV=A

Plot A vs Vid, will get the figure

 

[jonashat]

Use a balun for the input and output.
Vinp=Vid/2+Vic
Vinn=-Vid/2+Vic
Then give Vdm a dc sweep
plot the voltage of output node.
Use calculator to derive the output node. dVout/dV=A

Plot A vs Vid, will get the figure

And one last step, change the x axis from Vid to Vod