Logic levels and noise margins MCQs

What is the typical logic level voltage for a binary ‘1’ in TTL logic?

A 0V
B 2.5V
C 3.3V
D 5V
Answer: D 5V
What is the typical logic level voltage for a binary ‘0’ in CMOS logic operating at 5V?

A 0V
B 1.5V
C 2.5V
D 5V
Answer: A 0V
In a 3.3V CMOS system, what voltage range typically defines a logic ‘1’?

A 0V to 1.0V
B 1.0V to 2.3V
C 2.0V to 3.3V
D 3.0V to 3.3V
Answer: C 2.0V to 3.3V
What is the noise margin high (NMH) in a digital circuit?

A The difference between V_IL(max) and V_OH(min)
B The difference between V_IH(min) and V_OH(min)
C The difference between V_OH(min) and V_IH(min)
D The difference between V_IL(max) and V_OH(max)
Answer: C The difference between V_OH(min) and V_IH(min)
What is the noise margin low (NML) in a digital circuit?

A The difference between V_IL(max) and V_OL(max)
B The difference between V_OL(max) and V_IL(max)
C The difference between V_OL(min) and V_IL(min)
D The difference between V_OL(max) and V_IH(min)
Answer: B The difference between V_OL(max) and V_IL(max)
Which of the following defines the logic level threshold for a binary ‘0’ in TTL logic?

A 0V to 0.8V
B 0V to 1.0V
C 0V to 1.4V
D 0V to 2.0V
Answer: A 0V to 0.8V
In a 5V CMOS logic family, what voltage is typically considered a noise margin for high logic?

A 0.3V
B 0.7V
C 1.0V
D 1.3V
Answer: B 0.7V
What is the purpose of noise margins in digital circuits?

A To increase power consumption
B To ensure reliable operation despite electrical noise
C To decrease signal propagation delay
D To improve thermal stability
Answer: B To ensure reliable operation despite electrical noise
Which of the following voltage ranges would typically be considered invalid for logic levels in a 5V TTL system?

A 0V to 0.8V
B 1.4V to 1.6V
C 2.0V to 5.0V
D 4.5V to 5.0V
Answer: B 1.4V to 1.6V
What is the typical input low voltage (V_IL) threshold for a 3.3V CMOS logic circuit?

A 0V
B 0.8V
C 1.5V
D 2.0V
Answer: B 0.8V
For a digital system operating at 1.8V, what voltage is typically considered a logic high?

A 0.3V
B 0.9V
C 1.2V
D 1.8V
Answer: C 1.2V
Which of the following is a common cause of noise in digital circuits?

A Low power supply voltage
B Electromagnetic interference (EMI)
C High impedance state
D Logic level threshold
Answer: B Electromagnetic interference (EMI)
What is V_OH in the context of logic levels?

A Maximum output voltage for a logic high
B Minimum output voltage for a logic high
C Maximum output voltage for a logic low
D Minimum output voltage for a logic low
Answer: B Minimum output voltage for a logic high
What is V_OL in the context of logic levels?

A Maximum output voltage for a logic high
B Minimum output voltage for a logic high
C Maximum output voltage for a logic low
D Minimum output voltage for a logic low
Answer: C Maximum output voltage for a logic low
Why is it important to consider noise margins when designing digital circuits?

A To minimize power consumption
B To maximize clock speed
C To ensure data integrity and reliable performance
D To reduce manufacturing costs
Answer: C To ensure data integrity and reliable performance
What is the typical V_IH (minimum input high voltage) for a 5V TTL circuit?

A 2.0V
B 2.4V
C 2.7V
D 3.0V
Answer: B 2.0V
In a digital system, what is the term for the allowable range of voltage that can be reliably interpreted as a logic level?

A Threshold voltage
B Noise margin
C Signal range
D Voltage swing
Answer: B Noise margin
What happens if a digital signal falls within the undefined region between logic high and logic low thresholds?

A It is considered a logic high
B It is considered a logic low
C It may cause unpredictable behavior
D It is ignored by the circuit
Answer: C It may cause unpredictable behavior
In CMOS logic, why is there typically a larger noise margin compared to TTL logic?

A CMOS uses higher voltage levels
B CMOS circuits are more sensitive to noise
C CMOS has sharper switching characteristics
D CMOS has lower power consumption
Answer: C CMOS has sharper switching characteristics
What is the significance of V_IL and V_IH in digital logic circuits?

A They define power supply voltage ranges
B They determine acceptable voltage levels for logic states
C They indicate the noise margin levels
D They specify output drive capability
Answer: B They determine acceptable voltage levels for logic states

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Logic levels and noise margins MCQs
By: Prof. Dr. Fazal Rehman | Last updated: June 8, 2024

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