🔍 Key Concepts

• Bias voltage on a vacuum tube grid and how it sets the tube’s operating point on its characteristic curve • What is required for undistorted Class A operation of an AF (audio frequency) amplifier • Why plate dissipation limits are important in power amplifiers and how grid bias affects plate current

💭 Think About

• For each choice (A, B, C), ask yourself: Is this statement true in general about how grid bias affects a tube, or is it unrelated? • Think about what happens if the grid bias is set incorrectly: How does it affect distortion? How does it affect average plate current and heating? • Consider whether any one of A, B, or C is clearly false, or if all three describe real consequences or roles of grid bias in an AF power amplifier.

✅ Before You Answer

• Check in your tube theory notes how grid bias sets the quiescent (no-signal) plate current and thus the operating conditions. • Verify the condition for Class A operation: the tube must conduct for the entire signal cycle without clipping—how does grid bias ensure this? • Confirm whether limiting plate current to stay within rated plate dissipation is achieved in part by choosing an appropriate grid bias. If all three are valid effects of grid bias, then that affects how you view choice D.