Question
Which of the following components can be used to reduce thermal drift in crystal oscillators?
Answer Options
- A) NPO capacitors
- B) Toroidal inductors
- C) Wirewound resistors
- D) Non-inductive resistors
Correct Answer: A
Explanation
Thermal drift (changes in operating frequency due to temperature fluctuations) is a major problem in oscillators. While the quartz crystal itself is relatively stable, the surrounding components, particularly the tuning and coupling capacitors, change capacitance value with temperature (temperature coefficient), which pulls the oscillator frequency.
NPO capacitors (Negative-Positive-Zero coefficient) are ceramic capacitors designed specifically to have an extremely low temperature coefficient, meaning their capacitance value remains nearly constant across a wide temperature range. By using \text{NPO} capacitors in the frequency-determining network of an oscillator, temperature-induced capacitance changes are minimized, thereby greatly reducing thermal drift and enhancing frequency stability.
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