Hello, I am designing an astable multivibrator using a TLC271. When calculating the period, I take into account the typical values of Voh and Vol. However, when simulating with LTspice (using a model of the TLC271 in high bias), the period has an error of about 15%. I'm not sure if I am overlooking any other important consideration besides the actual values of Voh and Vol. I would appreciate some guidance.

 

Please post your LTspice file.

 

Here it is.

 

If would say if you are within ±20% of expected values you're doing well.

 

Hi VCab,
What is the target period and the High/Low times of your design specification?
E
This is what I see on LTS with your asc file, approx 2.355mSec

 

Hello, I am designing an astable multivibrator using a TLC271. When calculating the period, I take into account the typical values of Voh and Vol. However, when simulating with LTspice (using a model of the TLC271 in high bias), the period has an error of about 15%. I'm not sure if I am overlooking any other important consideration besides the actual values of Voh and Vol. I would appreciate some guidance.

Did you take into account the voltage drop of the diodes?

Just a note: don't get into the habit of using op-amps when you should be using comparators. One day you'll come unstuck! Some op-amps (TL071, for instance) do odd things when the output saturates, and some others (NE5534, for instance) have two diodes back-to-back between the inputs.

 

Please post your LTspice file.

Hi VCab,
What is the target period and the High/Low times of your design specification?
E
This is what I see on LTS with your asc file, approx 2.355mSec

View attachment 319328

I'm trying to achieve a period of 2 milliseconds.

 

Hi VCab
Use a 0.47uF at C1.
E

 

I'm trying to achieve a period of 2 milliseconds.

F=1/2ms=500Hz.
Target duty cycle?

If you don't need the negative voltage output, you could use single supply.
BTW-Opamp output isn't rail-to-rail.

 

F=1/2ms=500Hz.
Target duty cycle?

If you don't need the negative voltage output, you could use single supply.
BTW-Opamp output isn't rail-to-rail.

I need my duty cycle to range from 0.2 to 0.8. Therefore, I am attempting to obtain an expression for the period. Following another reply, I suspect the issue may stem from the diodes. However, the expression I obtained with that consideration exhibits greater error.

Edit: I require a negative output voltage, and I have already taken into account that the voltage is not rail-to-rail.