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LicenseComputer2. Digital-logic-and-microprocessorMCQsMcqs on Digital Logicset-4

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151. Which of the following logic families use bipolar transistors?

  1. TTL\text{TTL}
  2. NMOS\text{NMOS}
  3. GaAs\text{GaAs}
  4. CMOS\text{CMOS}
Show me the answer

Answer: 1. TTL\text{TTL}

Explanation:

  • TTL (Transistor-Transistor Logic) uses bipolar transistors, while NMOS and CMOS use MOSFETs.

152. Which of the following TTL subfamilies is the fastest?

  1. Standard TTL\text{Standard TTL}
  2. Schottky TTL\text{Schottky TTL}
  3. High-speed TTL\text{High-speed TTL}
  4. Low-speed TTL\text{Low-speed TTL}
Show me the answer

Answer: 2. Schottky TTL\text{Schottky TTL}

Explanation:

  • Schottky TTL is the fastest among the TTL subfamilies due to its use of Schottky diodes to reduce propagation delay.

153. The output 0 and 1 levels for TTL logic family are approximately:

  1. 0.1 and 5V0.1 \text{ and } 5V
  2. 0.9 and 1.75V0.9 \text{ and } 1.75V
  3. 0.6 and 3.5V0.6 \text{ and } 3.5V
  4. −1.75 and −0.9V-1.75 \text{ and } -0.9V
Show me the answer

Answer: 1. 0.1 and 5V0.1 \text{ and } 5V

Explanation:

  • In TTL logic, the output low level is approximately 0.1V, and the output high level is approximately 5V.

154. The functional capacity of SSI devices is:

  1. 1 to 11 gates1 \text{ to } 11 \text{ gates}
  2. 100 to 10,000 gates100 \text{ to } 10,000 \text{ gates}
  3. 12 to 99 gates12 \text{ to } 99 \text{ gates}
  4. More than 10,000 gates\text{More than } 10,000 \text{ gates}
Show me the answer

Answer: 1. 1 to 11 gates1 \text{ to } 11 \text{ gates}

Explanation:

  • SSI (Small-Scale Integration) devices typically contain 1 to 11 gates.

155. The functional capacity for LSI devices is:

  1. 1 to 11 gates1 \text{ to } 11 \text{ gates}
  2. 100 to 10,000 gates100 \text{ to } 10,000 \text{ gates}
  3. 12 to 99 gates12 \text{ to } 99 \text{ gates}
  4. More than 10,000 gates\text{More than } 10,000 \text{ gates}
Show me the answer

Answer: 4. More than 10,000 gates\text{More than } 10,000 \text{ gates}

Explanation:

  • LSI (Large-Scale Integration) devices contain more than 10,000 gates.

156. The time required for a pulse to decrease from 90% to 10% of its maximum value is known as:

  1. Rise time\text{Rise time}
  2. Binary level transition period\text{Binary level transition period}
  3. Decay time\text{Decay time}
  4. Propagation delay\text{Propagation delay}
Show me the answer

Answer: 3. Decay time\text{Decay time}

Explanation:

  • The time taken for a pulse to decrease from 90% to 10% of its maximum value is called decay time.

157. Which logic family dissipates the minimum power?

  1. DTL\text{DTL}
  2. ECL\text{ECL}
  3. TTL\text{TTL}
  4. CMOS\text{CMOS}
Show me the answer

Answer: 4. CMOS\text{CMOS}

Explanation:

  • CMOS (Complementary Metal-Oxide-Semiconductor) logic dissipates the least power among the given options.

158. Which TTL subfamily has the maximum speed?

  1. Standard TTL\text{Standard TTL}
  2. High-speed TTL\text{High-speed TTL}
  3. Schottky-clamped TTL\text{Schottky-clamped TTL}
  4. Low-power TTL\text{Low-power TTL}
Show me the answer

Answer: 3. Schottky-clamped TTL\text{Schottky-clamped TTL}

Explanation:

  • Schottky-clamped TTL is the fastest TTL subfamily due to its reduced propagation delay.

159. Which of the following is the first integrated logic family?

  1. RTL\text{RTL}
  2. TTL\text{TTL}
  3. DTL\text{DTL}
  4. MOS\text{MOS}
Show me the answer

Answer: 1. RTL\text{RTL}

Explanation:

  • RTL (Resistor-Transistor Logic) was the first integrated logic family.

160. Why are digital circuits easier to design than analog circuits?

  1. They do not control electricity precisely over a wide range\text{They do not control electricity precisely over a wide range}
  2. They are made in the form of ICs\text{They are made in the form of ICs}
  3. All elements of digital circuits are from the same family\text{All elements of digital circuits are from the same family}
  4. They are smaller in size\text{They are smaller in size}
Show me the answer

Answer: 1. They do not control electricity precisely over a wide range\text{They do not control electricity precisely over a wide range}

Explanation:

  • Digital circuits operate with discrete voltage levels (0 and 1), making them easier to design compared to analog circuits, which require precise control over a wide range of voltages.

161. Which of the following electronic components is not found in ordinary ICs?

  1. Diodes\text{Diodes}
  2. Transistors\text{Transistors}
  3. Resistors\text{Resistors}
  4. Inductors\text{Inductors}
Show me the answer

Answer: 4. Inductors\text{Inductors}

Explanation:

  • Inductors are rarely used in ICs due to their large size and difficulty in fabrication.

162. The fan-out capability of a digital building block can be defined as:

  1. The number of inputs that one output can transmit to\text{The number of inputs that one output can transmit to}
  2. The amount of cooling required for fanning the heat out\text{The amount of cooling required for fanning the heat out}
  3. The number of inputs that can transmit to one input\text{The number of inputs that can transmit to one input}
  4. The maximum power dissipation (heat generation) that the unit can stand\text{The maximum power dissipation (heat generation) that the unit can stand}
Show me the answer

Answer: 1. The number of inputs that one output can transmit to\text{The number of inputs that one output can transmit to}

Explanation:

  • Fan-out refers to the number of inputs that a single output can drive without degrading the signal.

163. What is the main advantage of using MOSFET rather than bipolar transistor circuitry in ICs?

  1. Much greater complexity (more components) than bipolar circuits; better economy\text{Much greater complexity (more components) than bipolar circuits; better economy}
  2. Higher operating speed than bipolar circuits\text{Higher operating speed than bipolar circuits}
  3. Fewer power supply connections are required with MOS ICs\text{Fewer power supply connections are required with MOS ICs}
  4. System designers are more familiar with MOS circuitry\text{System designers are more familiar with MOS circuitry}
Show me the answer

Answer: 1. Much greater complexity (more components) than bipolar circuits; better economy\text{Much greater complexity (more components) than bipolar circuits; better economy}

Explanation:

  • MOSFETs allow for greater complexity and integration in ICs, making them more economical for large-scale designs.

164. FETs are used in linear ICs to:

  1. Increase input resistance\text{Increase input resistance}
  2. Increase device complexity\text{Increase device complexity}
  3. Provide large resistance\text{Provide large resistance}
  4. A and B above\text{A and B above}
Show me the answer

Answer: 1. Increase input resistance\text{Increase input resistance}

Explanation:

  • FETs (Field-Effect Transistors) are used in linear ICs to increase input resistance, which reduces loading effects.

165. Resistor Ratio design is used in linear ICs because:

  1. Ratio increases input resistance\text{Ratio increases input resistance}
  2. Ratio increases amplifier gain\text{Ratio increases amplifier gain}
  3. Precise resistor values are not possible with IC processes\text{Precise resistor values are not possible with IC processes}
  4. All of the above\text{All of the above}
Show me the answer

Answer: 3. Precise resistor values are not possible with IC processes\text{Precise resistor values are not possible with IC processes}

Explanation:

  • Resistor ratio design is used because it is easier to control the ratio of resistors than their absolute values in IC fabrication.

166. A p-channel enhancement-type MOSFET performs much the same functions as a PNP transistor, except that:

  1. It operates much faster\text{It operates much faster}
  2. It is considerably larger\text{It is considerably larger}
  3. It is controlled by voltage rather than by current, so it requires very little current at the control terminal\text{It is controlled by voltage rather than by current, so it requires very little current at the control terminal}
  4. It is controlled by current than voltage like a bipolar transistor\text{It is controlled by current than voltage like a bipolar transistor}
Show me the answer

Answer: 3. It is controlled by voltage rather than by current, so it requires very little current at the control terminal\text{It is controlled by voltage rather than by current, so it requires very little current at the control terminal}

Explanation:

  • MOSFETs are voltage-controlled devices, unlike bipolar transistors, which are current-controlled.

167. What advantages do ICs have over discrete-device circuits due to their greater complexity (i.e., more circuitry in less area)?

  1. Smaller size\text{Smaller size}
  2. Lower cost\text{Lower cost}
  3. Higher reliability\text{Higher reliability}
  4. All of the above\text{All of the above}
Show me the answer

Answer: 4. All of the above\text{All of the above}

Explanation:

  • ICs offer smaller size, lower cost, and higher reliability compared to discrete-device circuits.

168. The radix of the binary number is:

  1. 33
  2. 22
  3. 11
  4. 1010
Show me the answer

Answer: 2. 22

Explanation:

  • The radix (base) of the binary number system is 2.

169. The number of binary bits required to represent a hexadecimal digit is:

  1. 33
  2. 66
  3. 44
  4. 88
Show me the answer

Answer: 3. 44

Explanation:

  • Each hexadecimal digit can be represented by 4 binary bits.

170. The logical expression A+B+C=DA + B + C = D represents:

  1. NAND gate\text{NAND gate}
  2. EX-OR gate\text{EX-OR gate}
  3. OR gate\text{OR gate}
  4. AND gate\text{AND gate}
Show me the answer

Answer: 3. OR gate\text{OR gate}

Explanation:

  • The expression A+B+C=DA + B + C = D represents an OR gate, where the output is high if any input is high.

171. The output of the following gate is 1 only if at least one of its inputs is 0:

  1. AND gate\text{AND gate}
  2. NAND gate\text{NAND gate}
  3. OR gate\text{OR gate}
  4. NOT gate\text{NOT gate}
Show me the answer

Answer: 2. NAND gate\text{NAND gate}

Explanation:

  • A NAND gate outputs 1 if at least one of its inputs is 0.

172. The 1’s complement of binary number 0.01011 is:

  1. 1.101001.10100
  2. 0.01100.0110
  3. 0.00100.0010
  4. −1.1101-1.1101
Show me the answer

Answer: 1. 1.101001.10100

Explanation:

  • The 1’s complement is obtained by inverting all bits: 0.01011→1.101000.01011 \rightarrow 1.10100.

173. The 2’s complement of binary number 0.01010 is:

  1. 1.101011.10101
  2. 1.101001.10100
  3. 0.101010.10101
  4. 0.101000.10100
Show me the answer

Answer: 2. 1.101001.10100

Explanation:

  • The 2’s complement is obtained by inverting all bits and adding 1: 0.01010→1.10101+1=1.101100.01010 \rightarrow 1.10101 + 1 = 1.10110. (Note: There seems to be a discrepancy in the options.)

174. A half-adder is also known as:

  1. AND circuit\text{AND circuit}
  2. NOR circuit\text{NOR circuit}
  3. NAND circuit\text{NAND circuit}
  4. EX-OR circuit\text{EX-OR circuit}
Show me the answer

Answer: 4. EX-OR circuit\text{EX-OR circuit}

Explanation:

  • A half-adder consists of an EX-OR gate for the sum and an AND gate for the carry.

175. The output of the following gate is 0 only if at least one of the inputs is 1:

  1. AND gate\text{AND gate}
  2. EX-OR gate\text{EX-OR gate}
  3. OR gate\text{OR gate}
  4. NOR gate\text{NOR gate}
Show me the answer

Answer: 4. NOR gate\text{NOR gate}

Explanation:

  • A NOR gate outputs 0 if at least one of its inputs is 1.

176. Which of the following Boolean algebra rules is wrong?

  1. 0+A=A0 + A = A
  2. A+A=AA + A = A
  3. 1+A=11 + A = 1
  4. 1⋅A=11 \cdot A = 1
Show me the answer

Answer: 4. 1⋅A=11 \cdot A = 1

Explanation:

  • The correct rule is 1⋅A=A1 \cdot A = A, not 1⋅A=11 \cdot A = 1.

177. The octal system has the radix of:

  1. 22
  2. 88
  3. 44
  4. 1010
Show me the answer

Answer: 2. 88

Explanation:

  • The octal number system has a radix (base) of 8.

178. The binary system has the radix of:

  1. 00
  2. 22
  3. 11
  4. 1010
Show me the answer

Answer: 2. 22

Explanation:

  • The binary number system has a radix (base) of 2.

179. Octal number system uses fundamental digits 0 to 7. 124 (octal) in decimal equivalent is equal to:

  1. 180180
  2. 8484
  3. 8282
  4. 8686
Show me the answer

Answer: 2. 8484

Explanation:

  • Converting octal 124 to decimal: 1×82+2×81+4×80=64+16+4=841 \times 8^2 + 2 \times 8^1 + 4 \times 8^0 = 64 + 16 + 4 = 84.

180. 92 (decimal) in the octal number system is equivalent to:

  1. 1288128_8
  2. 1328132_8
  3. 1308130_8
  4. 1348134_8
Show me the answer

Answer: 4. 1348134_8

Explanation:

  • Converting decimal 92 to octal:
    • 92 ÷ 8 = 11 with remainder 4
    • 11 ÷ 8 = 1 with remainder 3
    • 1 ÷ 8 = 0 with remainder 1
    • Thus, 92 in decimal is 134 in octal.

181. Four-digit binary quantity 1001 is represented in the decimal system by:

  1. 77
  2. 11
  3. 99
  4. 1313
Show me the answer

Answer: 3. 99

Explanation:

  • Converting binary 1001 to decimal:
    1×23+0×22+0×21+1×20=8+0+0+1=91 \times 2^3 + 0 \times 2^2 + 0 \times 2^1 + 1 \times 2^0 = 8 + 0 + 0 + 1 = 9.

182. Binary number 101101 is equivalent in decimal form to:

  1. 4141
  2. 4545
  3. 4343
  4. 4747
Show me the answer

Answer: 2. 4545

Explanation:

  • Converting binary 101101 to decimal:
    1×25+0×24+1×23+1×22+0×21+1×20=32+0+8+4+0+1=451 \times 2^5 + 0 \times 2^4 + 1 \times 2^3 + 1 \times 2^2 + 0 \times 2^1 + 1 \times 2^0 = 32 + 0 + 8 + 4 + 0 + 1 = 45.

183. Number 373₁₀ is equivalent in the binary system to:

  1. 101110101101110101
  2. 101010101101010101
  3. 100110101100110101
  4. 101110011101110011
Show me the answer

Answer: 1. 101110101101110101

Explanation:

  • Converting decimal 373 to binary:
    • 373 ÷ 2 = 186 remainder 1
    • 186 ÷ 2 = 93 remainder 0
    • 93 ÷ 2 = 46 remainder 1
    • 46 ÷ 2 = 23 remainder 0
    • 23 ÷ 2 = 11 remainder 1
    • 11 ÷ 2 = 5 remainder 1
    • 5 ÷ 2 = 2 remainder 1
    • 2 ÷ 2 = 1 remainder 0
    • 1 ÷ 2 = 0 remainder 1
    • Thus, 373 in decimal is 101110101 in binary.

184. According to Boolean algebra, A+A=A + A =

  1. AA
  2. A/nA/n
  3. NANA
  4. 11
Show me the answer

Answer: 1. AA

Explanation:

  • The Boolean identity A+A=AA + A = A is known as the idempotent law.

185. In Boolean algebra, A⋅A⋅A⋅A⋅A=A \cdot A \cdot A \cdot A \cdot A =

  1. AA
  2. A5A^5
  3. A/5A/5
  4. AA
Show me the answer

Answer: 1. AA

Explanation:

  • The Boolean identity A⋅A⋅A⋅A⋅A=AA \cdot A \cdot A \cdot A \cdot A = A is also an application of the idempotent law.

186. In Boolean algebra, A⋅0=A \cdot 0 =

  1. 11
  2. AA
  3. 00
  4. 1+A1 + A
Show me the answer

Answer: 3. 00

Explanation:

  • The Boolean identity A⋅0=0A \cdot 0 = 0 is known as the null law.

187. The simplification of AB+BC+BCAB + BC + BC gives:

  1. AB+BCAB + BC
  2. BC+BCBC + BC
  3. AB+BCAB + BC
  4. BB
Show me the answer

Answer: 1. AB+BCAB + BC

Explanation:

  • Simplifying AB+BC+BCAB + BC + BC:
    • Since BC+BC=BCBC + BC = BC, the expression reduces to AB+BCAB + BC.

188. Which of the following is not functionally a complete set?

  1. AND, OR\text{AND, OR}
  2. NOR\text{NOR}
  3. NAND\text{NAND}
  4. AND, OR, NOT\text{AND, OR, NOT}
Show me the answer

Answer: 1. AND, OR\text{AND, OR}

Explanation:

  • The set {AND, OR} is not functionally complete because it cannot implement all Boolean functions without the NOT operation.

189. Which of the following is not true?

  1. 0×0=00 \times 0 = 0
  2. 1×0=01 \times 0 = 0
  3. 0×1=10 \times 1 = 1
  4. 1×1=11 \times 1 = 1
Show me the answer

Answer: 3. 0×1=10 \times 1 = 1

Explanation:

  • The correct Boolean multiplication rule is 0×1=00 \times 1 = 0, not 1.

190. The reduced form of the Boolean expression (A+B)(A+C)(A + B)(A + C) is:

  1. AB+ACAB + AC
  2. AC+BAC + B
  3. A+B+CA + B + C
  4. A+BCA + BC
Show me the answer

Answer: 4. A+BCA + BC

Explanation:

  • Simplifying (A+B)(A+C)(A + B)(A + C) using the distributive law:
    A⋅A+A⋅C+B⋅A+B⋅C=A+AC+AB+BCA \cdot A + A \cdot C + B \cdot A + B \cdot C = A + AC + AB + BC.
    • Applying the absorption law: A+AC+AB+BC=A+BCA + AC + AB + BC = A + BC.

191. Which of the following is a universal gate?

  1. AND\text{AND}
  2. EX-OR\text{EX-OR}
  3. OR\text{OR}
  4. NAND\text{NAND}
Show me the answer

Answer: 4. NAND\text{NAND}

Explanation:

  • The NAND gate is a universal gate because it can be used to implement any other logic gate.

192. Which function in positive logic is equivalent to the OR function in negative logic?

  1. NOT\text{NOT}
  2. OR\text{OR}
  3. AND\text{AND}
  4. NOR\text{NOR}
Show me the answer

Answer: 3. AND\text{AND}

Explanation:

  • In negative logic, the OR function behaves like the AND function in positive logic.

193. Which of the following logic expressions is wrong?

  1. 1+0=11 + 0 = 1
  2. 1+0+1=11 + 0 + 1 = 1
  3. 1+1=01 + 1 = 0
  4. 1+1+1=11 + 1 + 1 = 1
Show me the answer

Answer: 3. 1+1=01 + 1 = 0

Explanation:

  • The correct Boolean addition rule is 1+1=11 + 1 = 1, not 0.

194. The m-bit parallel adder consists of:

  1. (m+1) full adders(m + 1) \text{ full adders}
  2. m−1 full addersm - 1 \text{ full adders}
  3. m2 full addersm^2 \text{ full adders}
  4. m full addersm \text{ full adders}
Show me the answer

Answer: 4. m full addersm \text{ full adders}

Explanation:

  • An m-bit parallel adder requires m full adders, one for each bit.

195. A flip-flop can store:

  1. 1 bit of data1 \text{ bit of data}
  2. 3 bits of data3 \text{ bits of data}
  3. 2 bits of data2 \text{ bits of data}
  4. 4 bits of data4 \text{ bits of data}
Show me the answer

Answer: 1. 1 bit of data1 \text{ bit of data}

Explanation:

  • A flip-flop is a 1-bit memory element.

196. A shift register can be used for:

  1. Parallel to serial conversion\text{Parallel to serial conversion}
  2. Digital delay line\text{Digital delay line}
  3. Serial to parallel conversion\text{Serial to parallel conversion}
  4. All of the above\text{All of the above}
Show me the answer

Answer: 4. All of the above\text{All of the above}

Explanation:

  • A shift register can perform parallel-to-serial conversion, serial-to-parallel conversion, and act as a digital delay line.

197. Semiconductor memory is:

  1. Somewhat larger than magnetic core memory\text{Somewhat larger than magnetic core memory}
  2. A volatile memory\text{A volatile memory}
  3. Somewhat larger than magnetic core memory\text{Somewhat larger than magnetic core memory}
  4. All of the above\text{All of the above}
Show me the answer

Answer: 2. A volatile memory\text{A volatile memory}

Explanation:

  • Semiconductor memory is typically volatile, meaning it loses its data when power is removed.

198. The logic 1 in a positive logic system is represented by:

  1. Zero voltage\text{Zero voltage}
  2. Higher voltage level\text{Higher voltage level}
  3. Lower voltage level\text{Lower voltage level}
  4. Negative voltage\text{Negative voltage}
Show me the answer

Answer: 2. Higher voltage level\text{Higher voltage level}

Explanation:

  • In a positive logic system, logic 1 is represented by a higher voltage level.

199. A combinational logic circuit used to send data coming from a single source to two or more separate destinations is called:

  1. Decoder\text{Decoder}
  2. Multiplexer\text{Multiplexer}
  3. Encoder\text{Encoder}
  4. Demultiplexer\text{Demultiplexer}
Show me the answer

Answer: 4. Demultiplexer\text{Demultiplexer}

Explanation:

  • A demultiplexer sends data from one input to one of several outputs based on control signals.

200. A logic circuit used to change a BCD number into an equivalent decimal number is:

  1. Decoder\text{Decoder}
  2. Multiplexer\text{Multiplexer}
  3. Encoder\text{Encoder}
  4. Code converter\text{Code converter}
Show me the answer

Answer: 1. Decoder\text{Decoder}

Explanation:

  • A BCD-to-decimal decoder converts a BCD number into its equivalent decimal representation.
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