Help me with learning Pspice in Orcad 10.5

Help me in Pspice

I'm learning Pspice in Orcad 10.5 . But it's hardly to understand something . Could you advice me something about it .
1. I created a basic pulse generator using IC 555 but output still constanst value ( about 2.5volt with 5 VDC source) . No difference from circuit in it's datasheet but it couldn't oscillate .
2. I created other pulse generator using two CMOS 4011 but it couldn't oscillate , too.
3. I using IC 4013 for my simple frequency divider (50Hz-->25Hz) but it's output still 2,3volt const . Or when I connect it's Set pin with a pulse generator , it work but Output low level always is 2.3volt (5VDC for VDD) while output high level about 4.5-4.8Volt
Thanks for help . I'll post my schematic later .

Re: Help me in Pspice

you might want to go and set initial conditions on the capacitor to zero volts.
You should be able to do this by going into the schematic and double-clicking on the
capacitor and setting the IC variable to zero.

You can also try select the "skip initial transient solution" option in the transient analysis setup.

I think the reason that you are seeing everything constant is because spice is calculating the equilibrium condition and using this as the initial condition for the node voltages. So when the transient analysis starts and you are already in equilibrium, then there is no change needed in any of the voltages. Does this make sense?
So try either setting the IC to zero on the capacitor or skip the initial transient solution.

Best regards,
\[v_c\]

Help me in Pspice

try to use HELP ..i m sure u will understand everything from HELP because i m also using PSPICE in ORCAD.

Re: Help me in Pspice

Kindly do upload your schematic to us all, maybe I can help.

Re: Help me in Pspice

there are several Tutorials on Pspice in the forum ..i suggest you take a look at them first

Re: Help me in Pspice

hi everyone,

I've tried to simulate some timer circuits and oscillators but none of them worked on orcad !!
I tried the proposals made here by checking "skip initial conditions" and many other stuff.
If anyone did simulate such circuits before then by all means do share with us.

thanks, salam.

Help me in Pspice

i think u should have a noise becuase this is an ideal circuit .
when i was at university i had the same problem .
i advise you to put a pulse with very short period to get an oscillation.
just try it .... may be it works

Re: Help me in Pspice

Hi,

Another tip is to set condensators "IC" parameter to 0 or to VCC value.

Regards

Re: Help me in Pspice

IT worked just fine
IC≡ initial charge !!!

Many thanks to everyone