In a grounded grid amplifier using a triode vacuum tube, the input signal is applied to:

In a grounded-grid amplifier configuration, the control grid is connected directly to ground (or RF ground). Because the grid is grounded, the input RF signal must be applied to the cathode to modulate the electron stream flowing from the cathode to the plate. This configuration is highly popular in amateur radio linear power amplifiers because the grounded grid acts as a Faraday shield between the input (cathode) and output (plate). This shielding significantly reduces the capacitance between the input and output, preventing unwanted self-oscillation without needing complex neutralization circuits. Distractors such as the control grid or plate describe other amplifier classes (like the standard grounded-cathode), where the input goes to the grid and output is taken from the plate. In a grounded-grid design, the signal must enter through the cathode.