3
\$\begingroup\$

I'm trying to build a basic square wave oscillator using an astable vibrator made with an op-amp for my Intro to Circuits class.

Unfortunately, I cannot get LTspice to simulate the oscillations.

I've tried a good chunk of the op-amps available. I've also tried varying resistor values, VCC and VEE, capacitance, transient settings, and the initial voltage on the capacitor. I can get this to somewhat simulate on Farstad, but how do I get it to simulate on LTspice?

Edit- I am aware that voltages attached to VCC and VEE have incorrect polarity, it still doesn't work if they are correct.

Edit2- The capacitance in 100 nF, voltage is read from the output of op-amp. Zooming in on the photo should help if you have difficulty reading some of the values.

Edit3- This is the latest version of LTspice running on a Windows 11 machine.

enter image description here

\$\endgroup\$
3
  • 2
    \$\begingroup\$ There are problems with Astables on the bench and on the sim .Old people have seen this but they cannot read your photo so cant answer your question. \$\endgroup\$
    – Autistic
    Commented Nov 15, 2023 at 4:23
  • 2
    \$\begingroup\$ The images don’t show up well, small and bad color scheme. \$\endgroup\$
    – GodJihyo
    Commented Nov 15, 2023 at 4:32
  • 1
    \$\begingroup\$ Also Win 7 isn't supported anymore. \$\endgroup\$
    – MiNiMe
    Commented Nov 15, 2023 at 5:03

1 Answer 1

Reset to default
5
\$\begingroup\$

Here is one problem: The output of the op-amp is connected to GND.

There may be other problems.

enter image description here

\$\endgroup\$
1
  • 2
    \$\begingroup\$ Taking the output off ground and changing my positive input resistors to lower values seemed to have fixed it, thank you. \$\endgroup\$
    – Jgely
    Commented Nov 15, 2023 at 6:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.