The DC bias in a Class A amplifier:

🔍 Key Concepts

• Class A amplifier operation and where the operating point (Q-point) is set on the characteristic curve • Relationship between grid voltage and cathode voltage in a vacuum-tube amplifier for normal conduction • What happens to tube current when the grid is made more negative or more positive with respect to the cathode

💭 Think About

• For a Class A tube amplifier to conduct for the entire input cycle, should the grid be biased so that the tube is already conducting with no signal, or just at cutoff? • If you make the grid increasingly negative relative to the cathode, does the plate (anode) current increase or decrease? What does that imply about typical bias polarity? • Which choice is consistent with a stable operating point roughly in the middle of the tube’s linear region?

✅ Before You Answer

• Verify how grid-to-cathode voltage (Vgk) is defined: grid potential minus cathode potential • Check tube characteristic curves: note the sign of Vgk values where the tube operates linearly for Class A service • Confirm that the chosen option matches the usual fixed or self-bias arrangement used in basic Class A audio/RF stages

The DC bias in a Class A amplifier:

Usually is negative as measured at the grid with respect to cathode

Usually is positive as measured at the grid with respect to cathode

Cannot be determined

None of the above

🔍 Key Concepts

💭 Think About

✅ Before You Answer