*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)  

In a sine wave oscillator, the goal is to generate a continuous, stable sine wave signal. The basic components required to achieve this are:

1. **Amplifier**: This component increases the amplitude of the signal to compensate for any losses in the circuit.
2. **Filter**: This component selects the desired frequency and ensures that the oscillator produces a pure sine wave at that frequency.
3. **Feedback Loop**: The output of the amplifier is fed back into the input through the filter, which sustains the oscillation at the desired frequency.

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

- **Feedback Loop**: The feedback loop is crucial because it allows the oscillator to maintain a continuous signal. The filter ensures that only the desired frequency is fed back, while the amplifier compensates for any signal loss, maintaining the oscillation.

### Why Other Choices Are Incorrect:

- **A: An amplifier and a divider**: A divider is not used in basic sine wave oscillators. Dividers are typically used in frequency synthesis to reduce frequency, not to sustain oscillations.

- **B: A frequency multiplier and a mixer**: These components are used to change frequencies, not to generate a stable sine wave. A frequency multiplier increases frequency, and a mixer combines signals, neither of which are necessary for basic oscillation.

- **C: A circulator and a filter operating in a feed-forward loop**: A circulator is a non-reciprocal three-port device used in RF applications, not in basic oscillators. A feed-forward loop does not provide the necessary feedback to sustain oscillations.

### Key Concept:

- **Barkhausen Criterion**: For sustained oscillations, the total loop gain must be equal to one, and the total phase shift around the loop must be zero or an integer multiple of $2\pi$ radians. This is achieved with a filter and an amplifier in a feedback loop.

Understanding these components and their roles in a sine wave oscillator will help you identify the correct configuration for generating stable oscillations.