FCC Element 6 – Radiotelegraph Operator License (T) Practice Test

To determine the operating grid bias in a self-biased RF amplifier stage, we must consider how grid biasing works in relation to the given plate voltage, plate current, grid current, and the grid-leak resistance.

In a self-biased configuration, the grid is biased negatively with respect to the cathode due to the DC voltage drop across the grid-leak resistor caused by the grid current. The total current flowing through the grid-leak resistor (which is the grid current) causes a voltage drop that affects the grid voltage.

First, we calculate the voltage drop across the grid-leak resistance using Ohm's Law. The voltage drop \( V_g \) across the grid-leak resistor can be calculated as follows:

\[ V_g = I_g \times R_g \]

Where:

- \( I_g \) (grid current) is 15 mA (or 0.015 A),

- \( R_g \) (grid-leak resistance) is 4000 ohms.

Calculating the voltage drop:

\[ V_g = 0.015 \, \text{A} \times 4000 \, \text{ohms} = 60 \, \text{V} \]

This