What voltage range is considered invalid by transistor-transistor logic (TTL)?

Transistor-Transistor Logic (TTL) defines specific voltage levels for logic states to ensure reliable function in digital circuits. The TTL standard specifies that a voltage level from 0 volts to 0.8 volts is considered a logic low (0), and a voltage level from 2 volts to 5 volts is considered a logic high (1).

In this context, the range of 0.8 to 2 volts falls within a region where the circuit is not definitively interpreting the signal as either a strong logic high or a strong logic low. This makes it an invalid state because it can lead to ambiguity in signal interpretation, resulting in unpredictable behavior in the circuit. Therefore, this range is crucial to identify as invalid in TTL to maintain proper functionality and logic interpretation in digital circuits.

Understanding the TTL voltage thresholds is essential for anyone working with digital electronics, as it helps in designing and troubleshooting circuits effectively.