*Question E7H12:
Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer?*  

*Correct Answer is  B: Provide the crystal with a specified parallel capacitance*  

### AI Response: (may contain errors)  

To ensure that a crystal oscillator operates at the frequency specified by the crystal manufacturer, the correct choice is:

**B: Provide the crystal with a specified parallel capacitance.**

### Explanation of the Correct Answer:
- **Crystal Frequency Control**: Crystal oscillators rely on the mechanical resonance of the crystal to determine their operating frequency. The specified parallel capacitance is crucial because it affects the load on the crystal, which in turn influences the oscillation frequency.
- **Load Capacitance**: The manufacturer specifies a load capacitance that the oscillator circuit should provide. If the load capacitance is not matched, the frequency can shift from the intended value.

### Why the Other Choices are Incorrect:
- **A: Provide the crystal with a specified parallel inductance**: 
  - While inductance can affect the overall circuit behavior, it is not the primary factor in determining the frequency of a crystal oscillator. Crystals are designed to operate with specific capacitance rather than inductance.

- **C: Bias the crystal at a specified voltage**: 
  - The voltage bias does not directly influence the frequency of oscillation. Instead, it is the circuit configuration and load capacitance that determine the frequency.

- **D: Bias the crystal at a specified current**: 
  - Similar to voltage, the current bias does not control the frequency. The frequency is primarily determined by the crystal's physical properties and the load capacitance.

### Useful Rules of Thumb:
- **Load Capacitance**: Always refer to the crystal's datasheet for the specified load capacitance to ensure proper operation.
- **Frequency Stability**: The stability of the oscillator frequency can be affected by temperature and other environmental factors, but the load capacitance is a key design parameter.

By understanding the role of load capacitance in crystal oscillators, you can ensure that your designs will operate at the desired frequencies as specified by the crystal manufacturer.