good circuit analysis program

chopficaro

im currently using protel to draw circuit diagrams and it is fine for that. but, when trouble shooting a board, i'd like to have a schematic drawing program that would allow me to set my own input voltages and allow me to check the voltages at different nodes. the only components i need it to recognize are amplifiers and resistors. if it could do capacitors that would also be helpful, but i only expect to find programs that do DC calculations.

i liked the way logicworks was set up, it allowed me to set the inputs and place probes everywhere i wanted to test the outputs, but that program was only for logic gates, and the voltages checked were 1's and 0's nothing more.

any suggestions would be greatly appreciated.

Redbelly98

LT Spice is good, and it's free:

http://www.linear.com/designtools/software/ltspice.jsp
and then click "No thanks, just download the software."

chopficaro

thank you, lt spice is working very well so far. but would you happen to know how to insert a potentiometer?

Bob S

I like LTSpice also. I have used a dc voltage source for a potentiometer in the past. You will have to re-run the simulation after every change.

Redbelly98

Using Bob S's suggestion of dc voltage source will work if it's a dc circuit. Otherwise, you'll have to add a potentiometer model.

I've not used the potentiometer model, but you can find it at the Yahoo group devoted to LT Spice. You'll have to sign up for a (free) Yahoo account if you don't already have one, then you can join the LT Spice group here:

http://tech.groups.yahoo.com/group/LTspice

After joining that group, click on "Files", then "Tut", then "Potentiometer".

From there, click on the "potentiometer_standard.txt " file to get directions for installing the potentiometer models. It basically tells you to copy two files into specific folders on your computer, then restart LT Spice for the changes to take effect.

I haven't used the potentiometer models before, so if it works out let us know!

Good luck.