The difference between open and closed loop circuits is that an open loop circuit is a control system where the output does not influence the input. It operates based on preset conditions without feedback, making it simple but less accurate and unable to correct errors. A fan with manual speed control is an example.

A closed loop circuit, on the other hand, uses feedback from the output to adjust the input and maintain the desired performance. This makes it more accurate and stable but also more complex. An air conditioner that automatically regulates room temperature is a good example.

The main difference is that closed loop systems correct themselves using feedback, while open loop systems do not.