Can someone tell me why do I get these results! Its transient analys of the circuit given below. I will try simulating the circuit with Orcad 16, but step by step. First the 1st operational amplifier and so on.

Here is step 1 and the results for different times, please pay attention to the times and to the graphic shape. This simulation is with Orcad 16 and I believe something is wrong with my Orcad.

 

I suspect the strange simulation results are caused by the significant mismatch between the timestep of the individual simulations and the signal that is present in the circuit.

You are only looking at the signal every 14ms or 29ms in the longer simulations and every 29us in the short simulation.

 

I suspect the strange simulation results are caused by the significant mismatch between the timestep of the individual simulations and the signal that is present in the circuit.

You are only looking at the signal every 14ms or 29ms in the longer simulations and every 29us in the short simulation.

How do you know this? And how do I change it?

 

I ran the simulation with the circuit in the attachements and Orcad 9.1 and it works . I get everything. I didnt add the last operational amplifier because I will exceed the 64 node limitation. But I still get all 3 signals. Is there any way to obtain a license for orcad 9.1?

 

Hello,

Why don't you try LTSpice?
It is free and unlimited:
http://www.linear.com/designtools/software/

It also has its own wiki:
http://ltwiki.org/index.php5?title=Main_Page

Many of our members are using it and the foum allows you to upload the .asc files that is used by LTSpice.

Bertus

 

I have been using orcad until now and I don't have the strength to learn a new tool.

 

How do you know this? And how do I change it?

It is shown in the images you provided with the "Timestep =". Look for somewhere to change the timestep or the number of points in the overall simulation. This should be accessible when setting up the simulation.

 

It is shown in the images you provided with the "Timestep =". Look for somewhere to change the timestep or the number of points in the overall simulation. This should be accessible when setting up the simulation.

This solved the problem! Thanks to everyone. I got some results that should be accurate, despite that they seem different from Orcad 9.1. I have Orcad 9.1 Schematics, but is there any way to get Layout, etc. and the full version of Orcad 9.1 even if its a student version?

 

How to mark this thread as solved?

These are the results after changing the transient simulation analisys to run to 100ms and with a maximum step of 1us instead of 1ms.