Hello. I try to ac simulation for AC analysis. I tried like attached file

ac dec 10 1 10M

and I want to see simulation result. It said

Transient op finished successfully

. but I can't see the graph of result. It said

no such vector cdac_vd

. I attached the image foe your reference. I thought command db() is problem. so I tried to simulated except many commands. Finally, I tried a simulation to using command like

plot v(cdac_vd)

but, It didn't work. How can I do to plot the AC analysis result? I appreciate for your help.

put the save all inside the .control (without the leading '.') , before the ac command.

.control
   ...
   save all
   ac ....
   write ...
   ...

.endc

You can use the

display

command at the ngspice prompt to see the available nodes. you can use vdb(node) instead of v(node) to display the value in dB, or ph(node) to get the phase (it is in radians, so you will often use plot ph(node)*180/pi )

@Stefan Schippers I tried simulation put the

save all

inside the

.control

but I think It has same error.

the

display

command should be given without any arguments at the ngspice prompt. You can use it to get the name of all saved waveforms. You will see if

cdac_vd

exists or not. Do not write into an ac_top.txt file, you should better keep the default extension, ac_top.raw, althouugh this is not an error.