*Question G7B11:
For which of the following modes is a Class C power stage appropriate for amplifying a modulated signal?*  

*Correct Answer is  B: FM*  

### AI Response: (may contain errors)  

To understand why a Class C power stage is appropriate for amplifying a modulated signal, let's break down the characteristics of Class C amplifiers and the modulation types listed in the question.

### Class C Amplifiers
- Class C amplifiers are designed to operate with a conduction angle of less than 180 degrees. This means they are "on" for less than half of the input signal cycle.
- They are highly efficient, making them suitable for applications where power efficiency is critical, such as in RF (radio frequency) transmission.

### Correct Answer: FM
- **Frequency Modulation (FM)**: Class C amplifiers are well-suited for FM signals because they can efficiently amplify the high-frequency components of the modulated signal. The efficiency of Class C amplifiers allows them to handle the rapid changes in frequency that characterize FM without significant distortion.

### Why Other Choices Are Incorrect
- **A: SSB (Single Sideband)**: While Class C amplifiers can be used for SSB, they are not the best choice because SSB requires linear amplification to preserve the integrity of the modulated signal. Class A or Class AB amplifiers are typically preferred for SSB due to their linearity.
  
- **B: AM (Amplitude Modulation)**: Similar to SSB, AM signals require linear amplification to maintain the amplitude variations of the signal. Class C amplifiers can introduce distortion in AM signals, making them less suitable for this type of modulation.

- **D: All these choices are correct**: This option is incorrect because, as explained, Class C amplifiers are not ideal for SSB and AM due to their non-linear characteristics.

### Summary
- Class C amplifiers are best for FM due to their efficiency and ability to handle high-frequency signals.
- SSB and AM require linear amplification, making Class A or Class AB amplifiers more appropriate for those modes.

In conclusion, the correct answer is FM because Class C amplifiers can efficiently amplify the frequency-modulated signals without significant distortion, unlike SSB and AM which require linear amplification.