LM2901 with PCA8575

Hi, I have designed a Non inverting comparator circuit with LM2901. The inverting input has 0.5V as Vref through a potential divider. The non inverting input is the signal input, which has 10K input resistor and a 390K feedback resistor to get 100mV hysteresis. The output has a 10K pull up and it is connected to a IO expander PCA8575 through a 0 ohm resistor. I am seeing a strange behavior of the comparator output. During power up, if the +input is 0V then the output is stuck at low. after power up, the change in the +input higher than Vref is not changing the state. However if the input is higher than Vref at the power up then the output is toggling high and low as expected. Can anyone help to explain what is happening here, and how to solve this issue?

by Sacra
December 11, 2021

Hope this would help you, you can find the LM2901 datasheet here: https://www.easybom.com/p/lm2901d-texas-instruments-3420391

by poppocat
December 21, 2021
Add comment...

Please sign in or create an account to comment.


No Answers

No answers yet. Contribute your answer below!


Your Answer

You must log in or create an account (free!) to answer a question.

Log in Create an account


Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

Search Questions & Answers


Ask a Question

Anyone can ask a question.

Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.


About This Site

CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.

We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.

Acceptable Questions:

  • Concept or theory questions
  • Practical engineering questions
  • “Homework” questions
  • Software/hardware intersection
  • Best practices
  • Design choices & component selection
  • Troubleshooting

Unacceptable Questions:

  • Non-English language content
  • Non-question discussion
  • Non-electronics questions
  • Vendor-specific topics
  • Pure software questions
  • CircuitLab software support

Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.