ACtE08 · Chapter 8Demo2 · Set 2🏛️ Past Licensure QuestionID: 8788f50c
In standard Transistor-Transistor Logic (TTL) circuits, what is the guaranteed voltage range for a recognized logic LOW (0) input level ()?
In standard Transistor-Transistor Logic (TTL) circuits, what is the guaranteed voltage range for a recognized logic LOW (0) input level ()?
Multiple Choice Options
- A✓ Correct Option
0 to 0.8 V
- B
2.0 to 5.0 V
- C
3.0 to 5.0 V
- D
5.0 to 12.0 V
Detailed Technical Solution & Explanation
For standard 7400-series TTL (Transistor-Transistor Logic) operating at a of :
•
Input Logic LOW ($V_{IL}$): Guaranteed to be interpreted as logic 0 from $0\text{ V}$ to $0.8\text{ V}$.
•
Input Logic HIGH ($V_{IH}$): Guaranteed to be interpreted as logic 1 from $2.0\text{ V}$ to $5.0\text{ V}$.
•
Indeterminate / Forbidden Zone: Voltages between and produce undefined logic behavior.
Option Analysis:
•
Option A (0 to 0.8 V): Correct; standard input voltage threshold for TTL logic LOW ().
•
Option B (2.0 to 5.0 V): Incorrect; defines the TTL input logic HIGH () threshold.
•
Option C (3.0 to 5.0 V): Incorrect; corresponds to 3.3V CMOS logic thresholds.
•
Option D (5.0 to 12.0 V): Incorrect; outside the maximum rating for 5V TTL ICs.
Reference: Demo2 · Set 2NEC Licensure Syllabus