*Question E7G03:
What is the typical input impedance of an op-amp?*  

*Correct Answer is  D: Very high*  

### AI Response: (may contain errors)  

The correct answer to the question about the typical input impedance of an op-amp is **D: Very high**.

### Explanation:

1. **Why the correct answer is correct:**
   - Operational amplifiers (op-amps) are designed to have a very high input impedance, typically in the range of megaohms (MΩ). This high input impedance is crucial because it allows the op-amp to draw minimal current from the input signal source, preventing loading effects that could alter the signal being measured or amplified. 

2. **Why the other choices are incorrect:**
   - **A: 100 ohms**: This value represents a low impedance, which is not characteristic of op-amps. Low input impedance would lead to significant loading of the source.
   - **B: 10,000 ohms**: While this is a higher impedance than 100 ohms, it is still considered low for op-amps. Most op-amps have input impedances much greater than this.
   - **C: Very low**: This is the opposite of what is true for op-amps. A very low input impedance would not be suitable for most applications where op-amps are used, as it would affect the performance and accuracy of the circuit.

### Useful Information:
- The input impedance of an op-amp can be approximated as:
  $$ Z_{in} \approx \frac{V_{out}}{I_{in}} $$
  where:
  - $Z_{in}$ = input impedance
  - $V_{out}$ = output voltage
  - $I_{in}$ = input current

- A rule of thumb is that the input impedance of an ideal op-amp is considered infinite, which is why they are used in applications requiring high input impedance. 

Understanding these concepts will help you grasp the fundamental characteristics of op-amps and their applications in circuits.