Definition

1. Noun:
   • A type of electronic vacuum tube: A "pentode" is a specific kind of thermionic valve (vacuum tube) containing five active electrodes inside an evacuated glass envelope. These electrodes are the cathode, control grid, screen grid, suppressor grid, and anode (plate). It is primarily used for amplification of electrical signals.

Usage and Examples

• Noun:
  • The audio amplifier used a pentode in its final stage for greater power output.
  • Compared to a triode, a pentode offers higher gain and better high-frequency performance.
  • Engineers replaced the worn-out pentode to restore the radio's functionality.

Advanced Usage

• Technical Context: In electronics, a "pentode" is often discussed in contrast to other vacuum tubes like diodes, triodes, and tetrodes, based on the number of electrodes. Its design minimizes a problem called secondary emission.
  • The suppressor grid in a pentode repels secondary electrons back to the anode.

Variants and Related Words

• Triode (n): A thermionic tube having three electrodes (cathode, grid, anode).
• Tetrode (n): A thermionic tube having four electrodes.
• Beam Pentode (n): A specialized type of pentode that uses beam-forming plates instead of a traditional suppressor grid to achieve similar effects.

Synonyms

• Vacuum Pentode: A more descriptive term emphasizing the tube's construction.
• Five-Electrode Tube: A direct, descriptive synonym.

Related Terms and Phrases

• "Pentode Connection": In some circuits, a tube like a pentode can be wired to function differently (e.g., as a triode) by connecting certain electrodes together.
  • Wiring the screen grid to the anode creates a triode connection for a sweeter sound.

Noun

1. a thermionic tube having five electrodes