Digital Logic

What is the voltage range considered to be a valid logic high input in a TTL device operating at 5.0 volts?

Answer

2.0 to 5.5 volts.

In 5-V TTL, an input from 2.0 to 5.5 V is guaranteed to be read as a valid logic high.

Source: FCC Element 3 question pool, 3E

Not the answer

  • 1.5 to 3.0 volts.
  • 5.2 to 34.8 volts.
  • 1.0 to 1.5 volts.

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