*Question G7B07:
Which of the following are basic components of a sine wave oscillator?*  

*Correct Answer is  D: A filter and an amplifier operating in a feedback loop*  

### AI Response: (may contain errors)  

To understand the basic components of a sine wave oscillator, let's break down the correct answer and the other choices.

### Correct Answer: D: A filter and an amplifier operating in a feedback loop

- **Explanation**: 
  - A sine wave oscillator typically consists of an amplifier and a filter arranged in a feedback loop. 
  - The amplifier boosts the signal, while the filter shapes the frequency of the output. 
  - The feedback loop ensures that a portion of the output is fed back into the input, allowing the oscillator to maintain a stable sine wave output.

### Why the Other Choices are Incorrect:

- **A: An amplifier and a divider**: 
  - While an amplifier is a key component, a divider is not typically used in a sine wave oscillator. Dividers are more common in frequency synthesis and digital circuits, not in generating sine waves.

- **B: A frequency multiplier and a mixer**: 
  - Frequency multipliers and mixers are used in signal processing and modulation, but they do not form the basic structure of a sine wave oscillator. They serve different purposes, such as changing frequency or combining signals.

- **C: A circulator and a filter operating in a feed-forward loop**: 
  - A circulator is a device used to control the direction of signal flow, often in RF applications, but it is not a fundamental component of a sine wave oscillator. Feed-forward loops are not standard in basic oscillator design.

### Useful Concepts:

- **Feedback Loop**: 
  - Essential for sustaining oscillations. The feedback must be positive (in-phase) to maintain the oscillation.

- **Barkhausen Criterion**: 
  - For an oscillator to start and maintain oscillation, the loop gain must be equal to or greater than one, and the total phase shift around the loop must be a multiple of $360^\circ$ (or $0^\circ$).

In summary, the correct answer highlights the essential components of a sine wave oscillator, while the other options do not align with the fundamental design principles of oscillators.