Powered by Invision Power Board


Forum Rules Forum Rules (Please read before posting)
  Reply to this topicStart new topicStart Poll

> Simple PSPICE netlist - all nodes floating?, Pspice netlist, however simple, not work
blindbiker
Posted: October 29, 2007 06:26 pm
Reply to this postQuote Post


Newbie
*

Group: Members+
Posts: 6
Member No.: 11,704
Joined: October 29, 2007




I have been getting back into Pspice, so I donwnloaded the evaluation version, and tried to simulate in the time domain, a very simple circuit with a Miller capacitor. I wanted to see how the slew rate depended on the Miller effect.

But when I try to run the simulation, I get a bunch of error messages. Here is the netlist:


CODE
* source SLEW RATE VS
R_R1         GND N00022  1k  
R_R2         N00007 5V  20k  
M_M3         N00007 N00022 GND GND IRF150
I_I1         N00022 GND DC 0Adc AC 0Aac
+PULSE 0 200uA 50us 50ns
C_C1         N00022 N00007  1n



And here are the errors:

CODE
ERROR -- Less than 2 connections at node 5V
ERROR -- Node GND is floating
ERROR -- Node N00022 is floating
ERROR -- Node N00007 is floating
ERROR -- Node 5V is floating


Thanks for your help!


(and BTW, this is the first post on this website ever - if I did something wrong posting-wise, cut me some slack, please)
PMEmail Poster
Top
fenugrec
Posted: October 29, 2007 11:25 pm
Reply to this postQuote Post


Sr. Member
*****

Group: Trusted Members
Posts: 488
Member No.: 5,637
Joined: July 13, 2006




It's been a while since I've manually entered spice stuff (and I've
never used PSPICE), but I think you need to define a voltage
source for your +5V.
PMUsers Website
Top
blindbiker
Posted: October 30, 2007 09:07 am
Reply to this postQuote Post


Newbie
*

Group: Members+
Posts: 6
Member No.: 11,704
Joined: October 29, 2007




QUOTE (fenugrec @ October 29, 2007 11:25 pm)

It's been a while since I've manually entered spice stuff (and I've
never used PSPICE), but I think you need to define a voltage
source for your +5V.

Thanks, smile.gif I believe that's it - I'll check when I get home today.

Thing is, I used the PSPICE capture tool to create the netlist, I didn't write it down manually. So I thought if I use the power symbol, PSPICE will take care of that actually, you know, being VCC. This PSPICE package is confusing, it seems to have two different ways of creating schematics. One is this I used, and is branded "OrCad", the other seems to be the original PSPICE one, but that's not integrated into the project - when you start a "project", you get to use the OrCad schem capture tool.

This stuff shouldn't be this confusing. I should be able to concentrate on the design, not the tool.

This post has been edited by blindbiker on October 30, 2007 09:08 am
PMEmail Poster
Top
blindbiker
Posted: October 30, 2007 04:23 pm
Reply to this postQuote Post


Newbie
*

Group: Members+
Posts: 6
Member No.: 11,704
Joined: October 29, 2007




QUOTE (fenugrec @ October 29, 2007 11:25 pm)
It's been a while since I've manually entered spice stuff (and I've
never used PSPICE), but I think you need to define a voltage
source for your +5V.

Well, I tried what you said. Apparently, that previous type of source doesn't have a single property - not even voltage??! So, I switched to another power component (you will see in the schematic). But that didn't do the trick:

user posted image

CODE

R_R1         GND N00022  1k  
R_R2         N00007 N00091  20k  
M_M3         N00007 N00022 GND GND IRF150
I_I1         N00022 GND DC 0Adc AC 0Aac
+PULSE 0 200uA 50us 50ns
V_V1         N00091 GND 5Vdc
C_C1         N00022 N00007  1n  
R_R3         N00022 N00007  910k  


ERROR -- Node GND is floating
ERROR -- Node N00022 is floating
ERROR -- Node N00007 is floating
ERROR -- Node N00091 is floating
PMEmail Poster
Top
fenugrec
Posted: October 31, 2007 01:03 am
Reply to this postQuote Post


Sr. Member
*****

Group: Trusted Members
Posts: 488
Member No.: 5,637
Joined: July 13, 2006




Don't know what to say. I entered the same schematic
in LTspice , this is the exported netlist:

CODE

V1 N001 0 5
R1 N001 N003 20k
R2 N003 N002 910k
C1 N003 N002 1n
R3 N002 0 1K
M1 N003 N002 0 0 NMOS
I1 0 N002 PULSE(0 200u 50u 50n 0 500u)


Only notable differences I see is that GND is named "0" here.
It seems PSPICE doesn't like your GND. I'm sure the program
includes examples that you can compare to yours; you could
also check out the documentation, might find something there.
PMUsers Website
Top
blindbiker
Posted: October 31, 2007 01:51 am
Reply to this postQuote Post


Newbie
*

Group: Members+
Posts: 6
Member No.: 11,704
Joined: October 29, 2007




QUOTE (fenugrec @ October 31, 2007 01:03 am)
Don't know what to say. I entered the same schematic
in LTspice , this is the exported netlist:

CODE

V1 N001 0 5
R1 N001 N003 20k
R2 N003 N002 910k
C1 N003 N002 1n
R3 N002 0 1K
M1 N003 N002 0 0 NMOS
I1 0 N002 PULSE(0 200u 50u 50n 0 500u)


Only notable differences I see is that GND is named "0" here.
It seems PSPICE doesn't like your GND. I'm sure the program
includes examples that you can compare to yours; you could
also check out the documentation, might find something there.

I entered the same schematic in PSPICE's "Schematic", instead of going the project-route. The "Schematics" program seems to be a separate schematics capture, different from the one named "Capture" (which does exactly the same thing but looks different and was developed by OrCad), and "Capture" is integrated in the whole project creation process, whereas "Schematic" isn't. Or at least, it doesn't seem to be.

But regardless of that, you can still make analyses, and analyze I did. Because "Schematic" accepted my netlist without reproach.

I love it when huge software packages are actually not even understood by their makers - this stuff has gotten so out of hand that nobody in the world knows anymore how these humongous packages really work and what they can do.

Anyway, rant off. Main thing is, I managed to enter my schematic (exactly the same way as I did in OrCad's "Capture") and there were no errors in the netlist, did my time-domain things and am almost happy. Of course, the actual circuit I am testing is much more complex than the 4-node NMOS stage.

LTspice? I'm going to try it right away.

This post has been edited by blindbiker on October 31, 2007 01:52 am
PMEmail Poster
Top
blindbiker
Posted: October 31, 2007 05:21 pm
Reply to this postQuote Post


Newbie
*

Group: Members+
Posts: 6
Member No.: 11,704
Joined: October 29, 2007




Tried LTspice. While just a little bit underpowered, it's very clear, very straightforward. There's nothing in there that I'd would wonder "how did this module end up in here, and what does it do?" So, it's going to be my Spice software for the time being, at least while I'm working from home.


Thanks for the eccellent hint!
PMEmail Poster
Top
Kai
Posted: February 20, 2012 07:31 pm
Reply to this postQuote Post


Newbie
*

Group: Members+
Posts: 1
Member No.: 36,544
Joined: February 20, 2012




I was having a similar error. I had to change the name of my ground (GND) to "0". Once I did that, all of my floating nodes, and my floating "GND" were taken care of. Kind of makes you wonder why the programmer didn't just make it set to 0 in the first place.... circuit won't work if you don't re-name the ground to 0.
PMEmail Poster
Top
Sch3mat1c
Posted: February 20, 2012 08:57 pm
Reply to this postQuote Post


Forum Addict ++
Group Icon

Group: Moderators
Posts: 19,586
Member No.: 73
Joined: July 24, 2002




SPICE defaults to '0' for ground. Some packages use GND for some reason; those that do *should* have an option to use 'GND' as the common node.

In a pinch, one could chuck in a "RGND 0 GND 1u" into the netlist to more-or-less short them together.

Tim


--------------------
Answering questions is a tricky subject to practice. Not due to the difficulty of formulating or locating answers, but due to the human inability of asking the right questions; a skill that, were one to possess, would put them in the "answering" category.
PMEmail PosterUsers Website
Top
MacFromOK
Posted: February 20, 2012 10:17 pm
Reply to this postQuote Post


Forum Addict ++
*******

Group: Spamminator Taskforce
Posts: 14,183
Member No.: 5,314
Joined: June 04, 2006




Yet another blast from the past... biggrin.gif


--------------------
Mac *

"Basic research is what I'm doing when I don't know what I'm doing." [Wernher Von Braun]

* is not responsible for errors, consequential damage, or... anything.
PMEmail Poster
Top
0 User(s) are reading this topic (0 Guests and 0 Anonymous Users)
0 Members:

Topic Options Reply to this topicStart new topicStart Poll

 


:: support us ::




ElectronicsSkin by DutchDork & The-Force