Refer the given figure. Which of the following describes the operation of the circuit?

A HIGH input turns Q1, Q2, and Q4 on; Q3 is off.

A LOW input turns Q1 and Q3 on; Q2 and Q4 are off.

A LOW input turns Q1 and Q4 off; Q2 and Q3 are on.

A HIGH input turns Q1, Q2, and Q3 off, and Q4 is on.

A HIGH input turns Q1, Q2, and Q4 on; Q3 is off.

What are the major differences between the 5400 and 7400 series of ICs?

The 7400 series are an improvement over the original 5400s.

The 5400 series are military grade and require tighter supply voltages and temperatures.

The 5400 series are military grade and allow for a wider range of supply voltages and temperatures.

The 7400 series are an improvement over the original 5400s.

The 7400 series was originally developed by Texas Instruments. The 5400 series was brought out by National Semiconductors after TI's patents expired, as a second supply source.

What is the full form of ECL in Integrated Circuit Logic Families?

It stands for energy-coupled logic; the input energy is amplified by the input transistors and allows the device to deliver higher output currents.

It stands for electron-coupled logic; all of the devices used within the gates are N-type transistors.

It stands for emitter-coupled logic; all of the inputs are coupled into the device through the emitters of the input transistors.

It stands for emitter-coupled logic; all of the emitters of the input transistors are connected together and each transistor functions as an emitter follower.

It stands for energy-coupled logic; the input energy is amplified by the input transistors and allows the device to deliver higher output currents.

What type of circuit is represented in the given figure, and which statement best describes its operation?

It is a programmable inverter. It can be programmed to function as either an active LOW or an active HIGH inverter.

It is a tristate inverter. When the ENABLE input is HIGH, the output is effectively an open circuit‚Äîit is neither LOW nor HIGH.

It is a programmable inverter. It can be programmed to function as either an active LOW or an active HIGH inverter.

It is an active LOW buffer, which can be turned on and off by the ENABLE input.

Propagation delay is important because ________.

it limits the maximum operating frequency of a gate

the logic gates must be given a short break during each clock cycle or else they will overheat

it limits the maximum operating frequency of a gate

it is a measure of how long the clock must be applied to the gate before it will make the required decision

all the gates in a system must have the same propagation times in order to be compatible

The bipolar TTL logic family that was developed to increase switching speed by preventing transistor saturation is:

transistor-transistor logic (TTL).

emitter-coupled logic (ECL) and transistor-transistor logic (TTL).

What must be done to interface TTL to CMOS?

A dropping resistor must be used on the CMOS 12 V supply to reduce it to 5 V for the TTL.

As long as the CMOS supply voltage is 5 V, they can be interfaced; however, the fan-out of the TTL is limited to five CMOS gates.

A 5 V Zener diode must be placed across the inputs of the TTL gates in order to protect them from the higher output voltages of the CMOS gates.

A pull-up resistor must be used between the TTL output-CMOS input node and Vcc; the value of RP will depend on the number of CMOS gates connected to the node.

What type of circuit is shown below, and how is the output ordinarily connected?

Any of the above could be correct, depending on the specific application involved.

It is an open-collector gate and is used to drive loads that cannot be connected directly to Vcc due to high noise levels.

It represents an active-LOW inverter and is used in negative logic systems.

It is an open-collector gate. An external load must be connected between the output terminal and an appropriate supply voltage.

Any of the above could be correct, depending on the specific application involved.

Whenever a totem-pole TTL output goes from LOW to HIGH, a high-amplitude current spike is drawn from the Vcc supply. How is this effect corrected to a digital circuit?

By using a switching power supply

By connecting a radio-frequency capacitor from Vcc to ground.

By using a switching power supply

By connecting a capacitor from Vout to ground

By connecting a large resistor from Vcc to Vout

Why is the fan-out of CMOS gates frequency dependent?

Each CMOS input gate has a specific propagation time and this limits the number of different gates that can be connected to the output of a CMOS gate.

When the frequency reaches the critical value, the gate will only be capable of delivering 70% of the normal output voltage and consequently the output power will be one-half of normal; this defines the upper operating frequency.

The higher the number of gates attached to the output, the more frequently they will have to be serviced, thus reducing the frequency at which each will be serviced with an input signal.

The input gates of the FETs are predominantly capacitive, and as the signal frequency increases the capacitive loading also increases, thereby limiting the number of loads that may be attached to the output of the driving gate.

A "floating" TTL input may be defined as:

unused input that is tied to Vcc through a 1 k resistor.

unused input that is tied to used inputs.

unused input that is tied to the ground.

unused input that is not connected.

Logic circuits that are designated as buffers, drivers, or buffer/drivers are designed to have:

greater input current/voltage capability than an ordinary logic circuit.

a greater current/voltage capability than an ordinary logic circuit.

greater input current/voltage capability than an ordinary logic circuit.

a smaller output current/voltage capability than an ordinary logic.

greater input and output current/voltage capability than an ordinary logic circuit.

What must be done to interface CMOS to TTL?

A 5 V Zener diode must be placed across the inputs of the TTL gates in order to protect them from the higher output voltages of the CMOS gates.

A dropping resistor must be used on the CMOS 12 V supply to reduce it to 5 V for the TTL.

As long as the CMOS supply voltage is 5 V, they can be interfaced; however, the fan-out of the CMOS is limited to two TTL gates.

A 5 V Zener diode must be placed across the inputs of the TTL gates in order to protect them from the higher output voltages of the CMOS gates.

The two series cannot be interfaced without the use of special interface buffers designed for that purpose, such as the open-collector buffers.

Which of the following summarizes the important features of ECL?

Good noise immunity, negative logic, high frequency capability, low power dissipation, and short propagation time

Low noise margin, low output voltage swing, negative voltage operation, fast, and high power consumption

Good noise immunity, negative logic, high frequency capability, low power dissipation, and short propagation time

Slow propagation time, high frequency response, low power consumption, and high output voltage swings

Poor noise immunity, positive supply voltage operation, good low frequency operation, and low power

What is unique about TTL devices such as the 74S00?

The gate transistors are silicon (S), and the gates therefore have lower values of leakage current.

The S denotes the fact that a single gate is present in the IC rather than the usual package of 2‚Äì6 gates.

The S denotes a slow version of the device, which is a consequence of its higher power rating.

The devices use Schottky transistors and diodes to prevent them from going into saturation; this results in faster turn on and turn off times, which translates into higher frequency operation.

Which of the following will not normally be found on a data sheet?

Maximum HIGH level input current

Minimum HIGH level output voltage

Maximum LOW level output voltage

Minimum LOW level output voltage

Maximum HIGH level input current

89 + Mcqs in Integrated Circuit Logic Families Page 2 McqOptions

51.	The IEEE/ANSI notation of an internal underlined diamond denotes:
A.	totem-pole outputs.
B.	open-collector outputs.
C.	quadrature amplifiers.
D.	tristate buffers.
Answer» C. quadrature amplifiers.

52.	The principal advantage of MOS ICs over TTL ICs is their fast operating speed.
A.	1
B.
C.	1
D.
Answer» C. 1

54.	A major drawback in using ECL logic circuits in conjunction with TTL and MOS circuits is its negative supply voltages and logic levels.
A.	1
B.
C.	1
D.
Answer» B.

55.	A ________ is a testing and troubleshooting tool that generates a short-duration pulse when manually activated, usually by depressing a push button.
A.	cattle prod
B.	jimmy rod
C.	logic pulser
D.	bilateral switch
Answer» D. bilateral switch

56.	________ output levels would not be a valid LOW for a TTL gate.
A.	0.2 V
B.	0.3 V
C.	0.5 V
D.	All of the above.
Answer» E.

57.	A logic signal experiences a delay in going through a circuit. The two propagation delay times are defined as:
A.	tPLH and tPHL.
B.	tDLH and tDHL.
C.	tHPL and tlph.
D.	tLDH and tHDL.
Answer» B. tDLH and tDHL.

58.	What type of logic circuit is shown below and what logic function is being performed?
A.	It is an NMOS AND gate.
B.	It is a CMOS AND gate.
C.	It is a CMOS NOR gate.
D.	It is a PMOS NAND gate.
Answer» D. It is a PMOS NAND gate.

60.	Generally, the voltage measured at an unused TTL input would typically be measured between:
A.	1.4 to 1.8 V.
B.	0 to 5 V.
C.	0 to 1.8 V.
D.	0.8 to 5 V.
Answer» B. 0 to 5 V.

61.	What is the static charge that can be stored by your body as you walk across a carpet?
A.	300 volts
B.	3,000 volts
C.	30,000 volts
D.	Over 30,000 volts
Answer» E.

63.	The noise immunity of a logic circuit refers to the circuit's ability to tolerate noise by causing spurious charges in the output voltage.
A.	1
B.
C.	1
D.
Answer» C. 1

66.	The output current for a LOW output is called a(n) ________.
A.	sink current
B.	ground current
C.	exit current
D.	fan-out
Answer» B. ground current

68.	Which of the logic families listed below allows the highest operating frequency?
A.	74AS
B.	ECL
C.	HCMOS
D.	54S
Answer» C. HCMOS

89.	Which of the following logic families has the highest maximum clock frequency?
A.	S-TTL
B.	AS-TTL
C.	HS-TTL
D.	HCMOS
Answer» C. HS-TTL

69.	The bipolar TTL logic family that was developed to increase switching speed by preventing transistor saturation is:
A.	emitter-coupled logic (ECL).
B.	current-mode logic (CML).
C.	transistor-transistor logic (TTL).
D.	emitter-coupled logic (ECL) and transistor-transistor logic (TTL).
Answer» E.

70.	What is the increase in switching speed between 74LS series TTL and 74HC/HCT (High-Speed CMOS)?
A.	5
B.	10
C.	50
D.	100
Answer» C. 50

71.	Which of the following logic families has the highest noise margin?
A.	TTL
B.	LS TTL
C.	CMOS
D.	HCMOS
Answer» E.

72.	The data sheet for the 74 series of TTL ICs shows that Vcc has a range of 4.5 V to 5.5 V.
A.	1
B.
Answer» C.

73.	The dc noise margins calculated using the proper values from a standard TTL data sheet are the worst-case margins. The typical dc noise margins are usually somewhat higher.
A.	1
B.
Answer» B.

74.	The abbreviated designator for a HIGH input voltage is VIH.
A.	1
B.
C.	1
D.
Answer» B.

77.	Several manufacturers have developed logic that combines the best features of TTL and CMOS. This is called ________.
A.	12L
B.	BiCMOS
C.	74ACT
D.	74HCT
Answer» C. 74ACT

78.	The minimum input voltage recognized as HIGH by a TTL gate is ________.
A.	2.0 V
B.	2.4 V
C.	0.8 V
D.	5.0 V
Answer» B. 2.4 V

81.	When the outputs of several open-collector TTL gates are connected together, the gate outputs ________.
A.	usually burn out
B.	produce more voltage
C.	are ANDed together
D.	produce more fan-out
Answer» D. produce more fan-out

85.	The major advantage of TTL logic circuits over CMOS is lower propagation delay.
A.	1
B.
C.	1
D.
Answer» B.

Explore topic-wise MCQs in Digital Electronics.

The IEEE/ANSI notation of an internal underlined diamond denotes:

The principal advantage of MOS ICs over TTL ICs is their fast operating speed.

Refer the given figure. Which of the following describes the operation of the circuit?

A major drawback in using ECL logic circuits in conjunction with TTL and MOS circuits is its negative supply voltages and logic levels.

A ________ is a testing and troubleshooting tool that generates a short-duration pulse when manually activated, usually by depressing a push button.

________ output levels would not be a valid LOW for a TTL gate.

A logic signal experiences a delay in going through a circuit. The two propagation delay times are defined as:

What type of logic circuit is shown below and what logic function is being performed?

The noise margin for TTL is 0.8 V.

Generally, the voltage measured at an unused TTL input would typically be measured between:

What is the static charge that can be stored by your body as you walk across a carpet?

What are the major differences between the 5400 and 7400 series of ICs?

The noise immunity of a logic circuit refers to the circuit's ability to tolerate noise by causing spurious charges in the output voltage.

What is the full form of ECL in Integrated Circuit Logic Families?

What type of circuit is represented in the given figure, and which statement best describes its operation?

The output current for a LOW output is called a(n) ________.

Propagation delay is important because ________.

Which of the logic families listed below allows the highest operating frequency?

The bipolar TTL logic family that was developed to increase switching speed by preventing transistor saturation is:

What is the increase in switching speed between 74LS series TTL and 74HC/HCT (High-Speed CMOS)?

Which of the following logic families has the highest noise margin?

The data sheet for the 74 series of TTL ICs shows that Vcc has a range of 4.5 V to 5.5 V.

The dc noise margins calculated using the proper values from a standard TTL data sheet are the worst-case margins. The typical dc noise margins are usually somewhat higher.

The abbreviated designator for a HIGH input voltage is VIH.

What must be done to interface TTL to CMOS?

What type of circuit is shown below, and how is the output ordinarily connected?

Several manufacturers have developed logic that combines the best features of TTL and CMOS. This is called ________.

The minimum input voltage recognized as HIGH by a TTL gate is ________.

Whenever a totem-pole TTL output goes from LOW to HIGH, a high-amplitude current spike is drawn from the Vcc supply. How is this effect corrected to a digital circuit?

Why is the fan-out of CMOS gates frequency dependent?

When the outputs of several open-collector TTL gates are connected together, the gate outputs ________.

A "floating" TTL input may be defined as:

Logic circuits that are designated as buffers, drivers, or buffer/drivers are designed to have:

What must be done to interface CMOS to TTL?

The major advantage of TTL logic circuits over CMOS is lower propagation delay.

Which of the following summarizes the important features of ECL?

What is unique about TTL devices such as the 74S00?

Which of the following will not normally be found on a data sheet?

Which of the following logic families has the highest maximum clock frequency?