LT-spice astable oscillator with inverter

Thread Starter

Jérémaguila

Joined Mar 9, 2023
8
Hello everyone,
I'm a beginner in Ltspice and i'm trying to simulate an astable oscillator (It's a pulse oscillator) base on a electrical circuit i found on internet.
The circuit is the following:
1679910918713.png
It's base on inverter and the period is approximately R1*C1.
I tried to simulate it using classical component in the LTspice library but the oscillation aren't starting and i obtain 0V at the output?
Here is my Ltspice circuit:
1679911185503.png
I build the invertor with the classic nmos and pmos of Ltspice
1679911385172.png

I hope you can help me with this issu
Thanks in advance for your time
kind regards
jeremie perque
 

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crutschow

Joined Mar 14, 2008
32,029
Below is the sim for the circuit with corrected errors and some modifications:
(I didn't use your inverter symbols.)
  1. Removed VCC (not connected or needed)
  2. Used real MOSFET models in place of the defaults (which can be flaky)
  3. Removed C1 and R2 (not needed)
  4. Added uic option to transient command (below) as simulated oscillators often don't start without that--
1679931293443.png
1679935954056.png
 
Last edited:

Thread Starter

Jérémaguila

Joined Mar 9, 2023
8
Thanks a lot for your answer and your time, it help me a lot. I will try your model.
By the way I retry the circuit using a more realistic model for NMOS and PMOS as you suggest and the oscillations started
1679987200300.png
Here are the MOS i used
1679987261259.png
I obtained some pulse oscillations:
1679987330680.png

So, maybe the inverter was to perfect to make the oscillations start.

Thanks again
Kind regard
 
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