*Question E6C02:
What happens when the level of a comparator’s input signal crosses the threshold voltage?*  

*Correct Answer is  B: The comparator changes its output state*  

### AI Response: (may contain errors)  

When studying comparators, it's important to understand their basic function and behavior:

1. **Correct Answer: B - The comparator changes its output state**

   - A comparator is an electronic device that compares two voltages or currents and outputs a digital signal indicating which is larger.
   - When the input signal crosses the threshold voltage, the comparator switches its output from one state to another. This is the primary function of a comparator: to detect when an input signal exceeds a certain reference level and to change its output accordingly.

2. **Why the other choices are incorrect:**

   - **A: The IC input can be damaged**
     - Comparators are designed to handle input signals crossing the threshold without damage. They are built to switch states safely when this occurs.
   
   - **C: The reference level appears at the output**
     - The reference level is used internally by the comparator to determine the output state but does not appear at the output. The output is a digital signal indicating the comparison result.
   
   - **D: The feedback loop becomes unstable**
     - Comparators typically do not have feedback loops like operational amplifiers in certain configurations. The crossing of the threshold does not inherently cause instability in a comparator.

3. **Useful Concepts:**

   - **Threshold Voltage ($V_{\text{th}}$):** The specific voltage level at which the comparator changes its output state.
   - **Output States:** Typically, a comparator has two output states, often represented as high (logic 1) and low (logic 0).

Understanding these concepts will help you recognize the role of a comparator in electronic circuits and why it behaves the way it does when the input signal crosses the threshold voltage.