🔍 Key Concepts

• Cathode-bias (self-bias): how raising the cathode above ground creates a negative grid-to-cathode voltage • Relationship between bias voltage, current, and resistance using Ohm’s Law • Difference between plate current and total cathode current (including screen current in tetrodes/pentodes)

💭 Think About

• How does the IR drop across the cathode resistor relate to the grid-to-cathode bias voltage? • When you know the desired DC bias voltage and the no-signal cathode current, how can Ohm’s Law help you find the needed resistance value? • For tubes with a screen (tetrodes/pentodes), which currents actually flow through the cathode resistor?

✅ Before You Answer

• Use Ohm’s Law: R = V / I with bias voltage and total no-signal cathode current • Remember that in tetrodes and pentodes, screen current also flows through the cathode, not just plate current • Check which options describe parts of the same correct method rather than different, conflicting methods