*Question E7H08:
Which of the following components can be used to reduce thermal drift in crystal oscillators?*  

*Correct Answer is  A: NP0 capacitors*  

### AI Response: (may contain errors)  

To understand why NP0 capacitors are the correct choice for reducing thermal drift in crystal oscillators, let's break down the options:

### Correct Answer: NP0 Capacitors
- **Why it's correct**: 
  - NP0 (also known as C0G) capacitors are made from a ceramic material that has a very low temperature coefficient. This means that their capacitance changes very little with temperature variations. In crystal oscillators, maintaining a stable frequency is crucial, and using NP0 capacitors helps minimize frequency drift caused by temperature changes.

### Incorrect Choices:
- **B: Toroidal Inductors**: 
  - While toroidal inductors are efficient and have low electromagnetic interference, they do not specifically address thermal drift. Their primary function is to store energy in a magnetic field, and they are not designed to stabilize frequency in oscillators.

- **C: Wirewound Resistors**: 
  - Wirewound resistors can have significant thermal drift due to the materials used in their construction. Their resistance can change with temperature, which can negatively impact the stability of the oscillator circuit.

- **D: Non-inductive Resistors**: 
  - Non-inductive resistors are designed to minimize inductance, which is beneficial in high-frequency applications. However, they still can exhibit thermal drift, and they do not provide the same level of temperature stability as NP0 capacitors.

### Summary
- **Key Takeaway**: NP0 capacitors are preferred in crystal oscillator circuits for their minimal temperature coefficient, which helps maintain frequency stability. Other components like toroidal inductors, wirewound resistors, and non-inductive resistors do not effectively reduce thermal drift.

This understanding will help you answer similar questions on the exam regarding component selection for stability in electronic circuits.