Trap Filter Design Notes

What is "Trap"

  • Band Eliminate Filter (B. E. F.) which blocks or attenuates particular frequency is called trap.
  • Contrariwise, ceramic filter passes only particular frequency. Sound trap for TV set is one of the famous example of B. E. F.
  • In TV set, video signal is used in picture amplitude circuit after video signal detection block, ceramic resonator is insert here and trap circuit is formed in order to eliminate sound signal involved in video signal.

Type of "Ceramic Trap"

    DeMint's Ceramic trap is divided into 2 types:

    1. Two-Terminal Ceramic Trap Filter:
      Two-terminal ceramic Trap is used in Black and White TV sets since the number of peripheral components can be reduced, though its attenuation isn't so much.

    2. Three-Terminal Ceramic Trap Filter:
      Three-terminal ceramic trap has a monolith structure formed from 2 ceramic resonators. The characteristic of a three-terminal ceramic trap equals two two-terminal ceramic trap. The three-terminal ceramic trap needs additional coil, it is used in Color TV set and VCR because to its high attenuation.

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