*Question E7B11:
In Figure E7-1, what is the purpose of R3?*  

*Correct Answer is  D: Self bias*  

### AI Response: (may contain errors)  

In Figure E7-1, the purpose of R3 is to provide **self bias** for a transistor circuit.

### Explanation:

1. **Correct Answer: Self bias (D)**
   - **Self bias** is a method used to establish a stable operating point for a transistor. R3 is typically connected in the emitter leg of a transistor circuit. It develops a voltage drop due to the emitter current, which in turn provides a stable biasing voltage. This helps maintain consistent transistor operation despite variations in temperature or transistor parameters.

2. **Why the other choices are incorrect:**
   - **Fixed bias (A):** Fixed bias involves using a separate voltage source or a fixed resistor connected to the base of the transistor. It does not rely on the emitter resistor (R3) for biasing.
   - **Emitter bypass (B):** An emitter bypass capacitor is used to increase the AC gain of a transistor amplifier by bypassing the emitter resistor at AC frequencies. R3 is not a capacitor, so it cannot serve this purpose.
   - **Output load resistor (C):** An output load resistor is typically connected to the collector of a transistor to develop the output signal. R3, being in the emitter leg, does not serve as an output load resistor.

### Useful Concept:

- **Self Biasing Formula:**
  - The voltage across R3 can be calculated as:
    $$ V_{R3} = I_E \times R3 $$
  - Where $I_E$ is the emitter current. This voltage helps set the base-emitter voltage ($V_{BE}$) and stabilizes the transistor's operating point.

Understanding the role of R3 in self biasing helps ensure stable transistor operation, which is crucial for reliable circuit performance.