*Question G7C08:
Which parameter affects receiver sensitivity?*  

*Correct Answer is  D: All these choices are correct*  

### AI Response: (may contain errors)  

Receiver sensitivity is a measure of a receiver's ability to detect weak signals. It is influenced by several factors, including:

1. **Input Amplifier Gain**:  
   - The gain of the input amplifier affects how much the incoming signal is amplified before further processing. Higher gain can improve sensitivity by making weak signals stronger, but it can also amplify noise.

2. **Demodulator Stage Bandwidth**:  
   - The bandwidth of the demodulator stage determines the range of frequencies that can pass through. A narrower bandwidth can improve sensitivity by reducing the amount of noise that enters the receiver, as noise power is proportional to bandwidth.

3. **Input Amplifier Noise Figure**:  
   - The noise figure of the input amplifier is a measure of how much noise the amplifier adds to the signal. A lower noise figure means less added noise, which improves sensitivity.

**Correct Answer: D: All these choices are correct**

- Each of these parameters—input amplifier gain, demodulator stage bandwidth, and input amplifier noise figure—affects receiver sensitivity. Therefore, all choices are correct.

**Why the other choices are incorrect individually:**

- **A: Input amplifier gain**: While gain is important, it alone does not determine sensitivity. Excessive gain can also increase noise.
- **B: Demodulator stage bandwidth**: Bandwidth affects sensitivity, but it must be considered alongside other factors like gain and noise figure.
- **C: Input amplifier noise figure**: A low noise figure is crucial for sensitivity, but it is not the only factor.

**Useful Formula:**

The sensitivity of a receiver can be estimated using the formula for the minimum discernible signal (MDS):

$$
\text{MDS} = \text{Noise Floor} + \text{Noise Figure} + 10 \log(\text{Bandwidth})
$$

- **Noise Floor**: Typically around -174 dBm/Hz at room temperature.
- **Noise Figure**: A measure of the noise added by the receiver.
- **Bandwidth**: The bandwidth of the receiver in hertz.

By understanding how each parameter affects sensitivity, you can better design and optimize a receiver for detecting weak signals.