*Question E7B05:
What can be done to prevent unwanted oscillations in an RF power amplifier?*  

*Correct Answer is  C: Install parasitic suppressors and/or neutralize the stage*  

### AI Response: (may contain errors)  

To prevent unwanted oscillations in an RF power amplifier, the correct approach is:

### Correct Answer: C: Install parasitic suppressors and/or neutralize the stage

1. **Why the correct answer is correct:**
   - **Parasitic Suppressors:** These are components, often resistors or ferrite beads, added to the circuit to dampen high-frequency oscillations that are not part of the desired signal. They help stabilize the amplifier by reducing the gain at frequencies where oscillations might occur.
   - **Neutralization:** This involves adding a feedback network to cancel out unwanted feedback that can cause oscillations. By neutralizing the stage, you effectively balance the circuit to prevent it from amplifying unintended signals.

### Why the other choices are incorrect:

- **A: Tune the stage for minimum loading**
  - Tuning for minimum loading does not address the root cause of oscillations. It might reduce power output but won't necessarily stop oscillations, which are often due to feedback or parasitic elements.

- **B: Tune both the input and output for maximum power**
  - While tuning for maximum power is generally desirable for efficiency, it does not prevent oscillations. In fact, maximizing power can sometimes exacerbate oscillations if the amplifier is unstable.

- **D: Use a phase inverter in the output filter**
  - A phase inverter is not typically used to prevent oscillations in RF amplifiers. It is more relevant in audio applications or for creating balanced signals, and does not address the feedback or parasitic issues that cause RF oscillations.

### Useful Concepts:

- **Parasitic Oscillations:** These are unwanted oscillations that occur at frequencies other than the intended operating frequency, often due to feedback paths or parasitic capacitance and inductance in the circuit.
- **Neutralization Techniques:** These involve creating a feedback path that is 180 degrees out of phase with the unwanted feedback, effectively canceling it out.

By focusing on parasitic suppressors and neutralization, you address the common causes of unwanted oscillations in RF power amplifiers.