# PSPICE Help: Integrating Op-Amp

#### random_digit

Joined Apr 21, 2007
8
Hello,

I'm working on a problem involving designing an ac integrator driven by a 10-V p-p square wave and using Probe to compare waveforms.

#### random_digit

Joined Apr 21, 2007
8
Well, I went over it again with a friend who is having the same problem. He found out that it is something with the non-inverting input.

So if I were to follow what you said Papabravo, I am to just delete this? Connect straight to ground?

#### JoeJester

Joined Apr 26, 2005
4,348
What signal are you using as the input? I know you said it was 10 volts pk-pk. Is that 5 volts plus and 5 volts minus? Is that 10 volts plus, 0 volts or the reverse of that?

What is the frequency of your 10 volt pk-pk signal?

#### random_digit

Joined Apr 21, 2007
8
I'm using a VPULSE part, going from -5V to 5V.

The problem has 2 parts, one simulation at 1 kHz and the other at 200 Hz. So under the part properties for the VPULSE I put 1/1000 for the PER, but to no avail. I can kind of guess what the waves are going to look like, but I need to have these waveforms present and printed out.

Thank you for all the help so far!

#### n9352527

Joined Oct 14, 2005
1,198
Create a netlist of your schematic and post it here.

#### random_digit

Joined Apr 21, 2007
8
* From [PSPICE NETLIST] section of pspiceev.ini:
.lib "nom.lib"

.INC "chap11.37.net"

**** INCLUDING chap11.37.net ****
* Schematics Netlist *

R_R1 $N_0002$N_0001 20k
R_Rf $N_0001$N_0003 50k
C_C $N_0001$N_0003 .1uF
V_V2 $N_0002 0 +PULSE -5V 5V 1ns 500ps 500ps 50ns .001s E_U1$N_0003 0 VALUE {LIMIT(V($N_0004,$N_0001)*1E6,-15V,+15V)}
R_Rc 0 $N_0004 14.2857k **** RESUMING chap11.37.cir **** .INC "chap11.37.als" **** INCLUDING chap11.37.als **** * Schematics Aliases * .ALIASES R_R1 R1(1=$N_0002 2=$N_0001 ) R_Rf Rf(1=$N_0001 2=$N_0003 ) C_C C(1=$N_0001 2=$N_0003 ) V_V2 V2(+=$N_0002 -=0 )
E_U1 U1(OUT=$N_0003 +=$N_0004 -=$N_0001 ) R_Rc Rc(1=0 2=$N_0004 )
.ENDALIASES

**** RESUMING chap11.37.cir ****
.probe

.END

ERROR -- Less than 2 connections at node $N_0004 #### n9352527 Joined Oct 14, 2005 1,198 Somehow in your netlist U1 is connected only to two nodes$N_0003 and 0 (ground), although your alias seems to understand this and is correct. U1 actually needs to be connected to three nodes, $N_0003,$N_0004 and \$N0001.

Check your schematic diagram, make sure all the nodes and wires are really connected and not just very near or on top of each other. Create a new netlist to confirm this.

#### JoeJester

Joined Apr 26, 2005
4,348
+PULSE -5V 5V 1ns 500ps 500ps 50ns .001s
I have questions about this. Your setting for a pulse width of 50 nS? I believe this exercise calls for a square wave, 50% duty cycle, at the two frequencies of interest.

This could be the reason for your "no output" condition, expecially if your attempting to view it over n milliseconds.