Hello:

I am trying to simulate a rising edge and falling edge detector using a CD4093 NAND gate
with Schmitt trigger inputs. I get the following message wrt the gate.

U1ut:b1"Unknown circuit node:"vdd" requested in behavioral source.

Can someone please tell me how to fix this?

Thanks

 

hi m.
It works OK for me?
E

 

hi m,
Press down an hold the Cntl key, right click mouse on the U1 symbol, check the VDD
E

 

U1ut:b1"Unknown circuit node:"vdd" requested in behavioral source.

You are apparently using the CMOS model library (.lib cd4000_V.lib) that needs a positive voltage source with its output node labeled "Vdd" (no quotes) to provide its power, so change the label +5V to Vdd.
Vdd can be any value from 3V to 15V, and the CMOS input logic and output voltage levels will correspond to that.

 

hi m,
Press down an hold the Cntl key, right click mouse on the U1 symbol, check the VDD
E
View attachment 313348

Hi E:

I did that for each of the 4 gates and changed the vdd to 5. Still not working for me.

 

hi m,
Try what @crutschow suggested.
E

There are a number of different versions of the CD4000 lib, the suffix v version needs the VDD that was noted.
E

 

hi m,
Look in your LTSpice folder, it should be in Documents, find the lib folder, look and see which CD4000.libs you have in the folder.
E

 

hi m,
Try this version.
Using cd4000_v.lib
Note the VDD.
E

 

hi m,
Look in your LTSpice folder, it should be in Documents, find the lib folder, look and see which CD4000.libs you have in the folder.
E

I am now using the CD4000.lib and the issue is resolved. Thanks both of you!
I also tweaked the circuit to get the pulses.