> For the complete documentation index, see [llms.txt](https://nec-license.gitbook.io/books/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://nec-license.gitbook.io/books/2.-digital-logic-and-microprocessor/mcqs/mcqs-on-digital-logic/set-4.md).
# set-4
#### 151. Which of the following logic families use bipolar transistors?
1. $$\text{TTL}$$
2. $$\text{NMOS}$$
3. $$\text{GaAs}$$
4. $$\text{CMOS}$$
Show me the answer
**Answer:** 1. $$\text{TTL}$$
**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. $$\text{Standard TTL}$$
2. $$\text{Schottky TTL}$$
3. $$\text{High-speed TTL}$$
4. $$\text{Low-speed TTL}$$
Show me the answer
**Answer:** 2. $$\text{Schottky TTL}$$
**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. $$0.1 \text{ and } 5V$$
2. $$0.9 \text{ and } 1.75V$$
3. $$0.6 \text{ and } 3.5V$$
4. $$-1.75 \text{ and } -0.9V$$
Show me the answer
**Answer:** 1. $$0.1 \text{ and } 5V$$
**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. $$1 \text{ to } 11 \text{ gates}$$
2. $$100 \text{ to } 10,000 \text{ gates}$$
3. $$12 \text{ to } 99 \text{ gates}$$
4. $$\text{More than } 10,000 \text{ gates}$$
Show me the answer
**Answer:** 1. $$1 \text{ to } 11 \text{ gates}$$
**Explanation:**
* SSI (Small-Scale Integration) devices typically contain 1 to 11 gates.
#### 155. The functional capacity for LSI devices is:
1. $$1 \text{ to } 11 \text{ gates}$$
2. $$100 \text{ to } 10,000 \text{ gates}$$
3. $$12 \text{ to } 99 \text{ gates}$$
4. $$\text{More than } 10,000 \text{ gates}$$
Show me the answer
**Answer:** 4. $$\text{More than } 10,000 \text{ gates}$$
**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. $$\text{Rise time}$$
2. $$\text{Binary level transition period}$$
3. $$\text{Decay time}$$
4. $$\text{Propagation delay}$$
Show me the answer
**Answer:** 3. $$\text{Decay time}$$
**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. $$\text{DTL}$$
2. $$\text{ECL}$$
3. $$\text{TTL}$$
4. $$\text{CMOS}$$
Show me the answer
**Answer:** 4. $$\text{CMOS}$$
**Explanation:**
* CMOS (Complementary Metal-Oxide-Semiconductor) logic dissipates the least power among the given options.
#### 158. Which TTL subfamily has the maximum speed?
1. $$\text{Standard TTL}$$
2. $$\text{High-speed TTL}$$
3. $$\text{Schottky-clamped TTL}$$
4. $$\text{Low-power TTL}$$
Show me the answer
**Answer:** 3. $$\text{Schottky-clamped TTL}$$
**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. $$\text{RTL}$$
2. $$\text{TTL}$$
3. $$\text{DTL}$$
4. $$\text{MOS}$$
Show me the answer
**Answer:** 1. $$\text{RTL}$$
**Explanation:**
* RTL (Resistor-Transistor Logic) was the first integrated logic family.
#### 160. Why are digital circuits easier to design than analog circuits?
1. $$\text{They do not control electricity precisely over a wide range}$$
2. $$\text{They are made in the form of ICs}$$
3. $$\text{All elements of digital circuits are from the same family}$$
4. $$\text{They are smaller in size}$$
Show me the answer
**Answer:** 1. $$\text{They do not control electricity precisely over a wide range}$$
**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. $$\text{Diodes}$$
2. $$\text{Transistors}$$
3. $$\text{Resistors}$$
4. $$\text{Inductors}$$
Show me the answer
**Answer:** 4. $$\text{Inductors}$$
**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. $$\text{The number of inputs that one output can transmit to}$$
2. $$\text{The amount of cooling required for fanning the heat out}$$
3. $$\text{The number of inputs that can transmit to one input}$$
4. $$\text{The maximum power dissipation (heat generation) that the unit can stand}$$
Show me the answer
**Answer:** 1. $$\text{The number of inputs that one output can transmit to}$$
**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. $$\text{Much greater complexity (more components) than bipolar circuits; better economy}$$
2. $$\text{Higher operating speed than bipolar circuits}$$
3. $$\text{Fewer power supply connections are required with MOS ICs}$$
4. $$\text{System designers are more familiar with MOS circuitry}$$
Show me the answer
**Answer:** 1. $$\text{Much greater complexity (more components) than bipolar circuits; better economy}$$
**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. $$\text{Increase input resistance}$$
2. $$\text{Increase device complexity}$$
3. $$\text{Provide large resistance}$$
4. $$\text{A and B above}$$
Show me the answer
**Answer:** 1. $$\text{Increase input resistance}$$
**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. $$\text{Ratio increases input resistance}$$
2. $$\text{Ratio increases amplifier gain}$$
3. $$\text{Precise resistor values are not possible with IC processes}$$
4. $$\text{All of the above}$$
Show me the answer
**Answer:** 3. $$\text{Precise resistor values are not possible with IC processes}$$
**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. $$\text{It operates much faster}$$
2. $$\text{It is considerably larger}$$
3. $$\text{It is controlled by voltage rather than by current, so it requires very little current at the control terminal}$$
4. $$\text{It is controlled by current than voltage like a bipolar transistor}$$
Show me the answer
**Answer:** 3. $$\text{It is controlled by voltage rather than by current, so it requires very little current at the control terminal}$$
**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. $$\text{Smaller size}$$
2. $$\text{Lower cost}$$
3. $$\text{Higher reliability}$$
4. $$\text{All of the above}$$
Show me the answer
**Answer:** 4. $$\text{All of the above}$$
**Explanation:**
* ICs offer smaller size, lower cost, and higher reliability compared to discrete-device circuits.
#### 168. The radix of the binary number is:
1. $$3$$
2. $$2$$
3. $$1$$
4. $$10$$
Show me the answer
**Answer:** 2. $$2$$
**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. $$3$$
2. $$6$$
3. $$4$$
4. $$8$$
Show me the answer
**Answer:** 3. $$4$$
**Explanation:**
* Each hexadecimal digit can be represented by 4 binary bits.
#### 170. The logical expression $$A + B + C = D$$ represents:
1. $$\text{NAND gate}$$
2. $$\text{EX-OR gate}$$
3. $$\text{OR gate}$$
4. $$\text{AND gate}$$
Show me the answer
**Answer:** 3. $$\text{OR gate}$$
**Explanation:**
* The expression $$A + B + C = D$$ 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. $$\text{AND gate}$$
2. $$\text{NAND gate}$$
3. $$\text{OR gate}$$
4. $$\text{NOT gate}$$
Show me the answer
**Answer:** 2. $$\text{NAND gate}$$
**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. $$1.10100$$
2. $$0.0110$$
3. $$0.0010$$
4. $$-1.1101$$
Show me the answer
**Answer:** 1. $$1.10100$$
**Explanation:**
* The 1's complement is obtained by inverting all bits: $$0.01011 \rightarrow 1.10100$$.
#### 173. The 2's complement of binary number 0.01010 is:
1. $$1.10101$$
2. $$1.10100$$
3. $$0.10101$$
4. $$0.10100$$
Show me the answer
**Answer:** 2. $$1.10100$$
**Explanation:**
* The 2's complement is obtained by inverting all bits and adding 1: $$0.01010 \rightarrow 1.10101 + 1 = 1.10110$$. (Note: There seems to be a discrepancy in the options.)
#### 174. A half-adder is also known as:
1. $$\text{AND circuit}$$
2. $$\text{NOR circuit}$$
3. $$\text{NAND circuit}$$
4. $$\text{EX-OR circuit}$$
Show me the answer
**Answer:** 4. $$\text{EX-OR circuit}$$
**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. $$\text{AND gate}$$
2. $$\text{EX-OR gate}$$
3. $$\text{OR gate}$$
4. $$\text{NOR gate}$$
Show me the answer
**Answer:** 4. $$\text{NOR gate}$$
**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. $$0 + A = A$$
2. $$A + A = A$$
3. $$1 + A = 1$$
4. $$1 \cdot A = 1$$
Show me the answer
**Answer:** 4. $$1 \cdot A = 1$$
**Explanation:**
* The correct rule is $$1 \cdot A = A$$, not $$1 \cdot A = 1$$.
#### 177. The octal system has the radix of:
1. $$2$$
2. $$8$$
3. $$4$$
4. $$10$$
Show me the answer
**Answer:** 2. $$8$$
**Explanation:**
* The octal number system has a radix (base) of 8.
#### 178. The binary system has the radix of:
1. $$0$$
2. $$2$$
3. $$1$$
4. $$10$$
Show me the answer
**Answer:** 2. $$2$$
**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. $$180$$
2. $$84$$
3. $$82$$
4. $$86$$
Show me the answer
**Answer:** 2. $$84$$
**Explanation:**
* Converting octal 124 to decimal: $$1 \times 8^2 + 2 \times 8^1 + 4 \times 8^0 = 64 + 16 + 4 = 84$$.
#### 180. 92 (decimal) in the octal number system is equivalent to:
1. $$128\_8$$
2. $$132\_8$$
3. $$130\_8$$
4. $$134\_8$$
Show me the answer
**Answer:** 4. $$134\_8$$
**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. $$7$$
2. $$1$$
3. $$9$$
4. $$13$$
Show me the answer
**Answer:** 3. $$9$$
**Explanation:**
* Converting binary 1001 to decimal:\
$$1 \times 2^3 + 0 \times 2^2 + 0 \times 2^1 + 1 \times 2^0 = 8 + 0 + 0 + 1 = 9$$.
#### 182. Binary number 101101 is equivalent in decimal form to:
1. $$41$$
2. $$45$$
3. $$43$$
4. $$47$$
Show me the answer
**Answer:** 2. $$45$$
**Explanation:**
* Converting binary 101101 to decimal:\
$$1 \times 2^5 + 0 \times 2^4 + 1 \times 2^3 + 1 \times 2^2 + 0 \times 2^1 + 1 \times 2^0 = 32 + 0 + 8 + 4 + 0 + 1 = 45$$.
#### 183. Number 373₁₀ is equivalent in the binary system to:
1. $$101110101$$
2. $$101010101$$
3. $$100110101$$
4. $$101110011$$
Show me the answer
**Answer:** 1. $$101110101$$
**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, $$A + A =$$
1. $$A$$
2. $$A/n$$
3. $$NA$$
4. $$1$$
Show me the answer
**Answer:** 1. $$A$$
**Explanation:**
* The Boolean identity $$A + A = A$$ is known as the idempotent law.
#### 185. In Boolean algebra, $$A \cdot A \cdot A \cdot A \cdot A =$$
1. $$A$$
2. $$A^5$$
3. $$A/5$$
4. $$A$$
Show me the answer
**Answer:** 1. $$A$$
**Explanation:**
* The Boolean identity $$A \cdot A \cdot A \cdot A \cdot A = A$$ is also an application of the idempotent law.
#### 186. In Boolean algebra, $$A \cdot 0 =$$
1. $$1$$
2. $$A$$
3. $$0$$
4. $$1 + A$$
Show me the answer
**Answer:** 3. $$0$$
**Explanation:**
* The Boolean identity $$A \cdot 0 = 0$$ is known as the null law.
#### 187. The simplification of $$AB + BC + BC$$ gives:
1. $$AB + BC$$
2. $$BC + BC$$
3. $$AB + BC$$
4. $$B$$
Show me the answer
**Answer:** 1. $$AB + BC$$
**Explanation:**
* Simplifying $$AB + BC + BC$$:
* Since $$BC + BC = BC$$, the expression reduces to $$AB + BC$$.
#### 188. Which of the following is not functionally a complete set?
1. $$\text{AND, OR}$$
2. $$\text{NOR}$$
3. $$\text{NAND}$$
4. $$\text{AND, OR, NOT}$$
Show me the answer
**Answer:** 1. $$\text{AND, OR}$$
**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. $$0 \times 0 = 0$$
2. $$1 \times 0 = 0$$
3. $$0 \times 1 = 1$$
4. $$1 \times 1 = 1$$
Show me the answer
**Answer:** 3. $$0 \times 1 = 1$$
**Explanation:**
* The correct Boolean multiplication rule is $$0 \times 1 = 0$$, not 1.
#### 190. The reduced form of the Boolean expression $$(A + B)(A + C)$$ is:
1. $$AB + AC$$
2. $$AC + B$$
3. $$A + B + C$$
4. $$A + BC$$
Show me the answer
**Answer:** 4. $$A + BC$$
**Explanation:**
* Simplifying $$(A + B)(A + C)$$ using the distributive law:\
$$A \cdot A + A \cdot C + B \cdot A + B \cdot C = A + AC + AB + BC$$.
* Applying the absorption law: $$A + AC + AB + BC = A + BC$$.
#### 191. Which of the following is a universal gate?
1. $$\text{AND}$$
2. $$\text{EX-OR}$$
3. $$\text{OR}$$
4. $$\text{NAND}$$
Show me the answer
**Answer:** 4. $$\text{NAND}$$
**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. $$\text{NOT}$$
2. $$\text{OR}$$
3. $$\text{AND}$$
4. $$\text{NOR}$$
Show me the answer
**Answer:** 3. $$\text{AND}$$
**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. $$1 + 0 = 1$$
2. $$1 + 0 + 1 = 1$$
3. $$1 + 1 = 0$$
4. $$1 + 1 + 1 = 1$$
Show me the answer
**Answer:** 3. $$1 + 1 = 0$$
**Explanation:**
* The correct Boolean addition rule is $$1 + 1 = 1$$, not 0.
#### 194. The m-bit parallel adder consists of:
1. $$(m + 1) \text{ full adders}$$
2. $$m - 1 \text{ full adders}$$
3. $$m^2 \text{ full adders}$$
4. $$m \text{ full adders}$$
Show me the answer
**Answer:** 4. $$m \text{ full adders}$$
**Explanation:**
* An m-bit parallel adder requires m full adders, one for each bit.
#### 195. A flip-flop can store:
1. $$1 \text{ bit of data}$$
2. $$3 \text{ bits of data}$$
3. $$2 \text{ bits of data}$$
4. $$4 \text{ bits of data}$$
Show me the answer
**Answer:** 1. $$1 \text{ bit of data}$$
**Explanation:**
* A flip-flop is a 1-bit memory element.
#### 196. A shift register can be used for:
1. $$\text{Parallel to serial conversion}$$
2. $$\text{Digital delay line}$$
3. $$\text{Serial to parallel conversion}$$
4. $$\text{All of the above}$$
Show me the answer
**Answer:** 4. $$\text{All of the above}$$
**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. $$\text{Somewhat larger than magnetic core memory}$$
2. $$\text{A volatile memory}$$
3. $$\text{Somewhat larger than magnetic core memory}$$
4. $$\text{All of the above}$$
Show me the answer
**Answer:** 2. $$\text{A volatile memory}$$
**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. $$\text{Zero voltage}$$
2. $$\text{Higher voltage level}$$
3. $$\text{Lower voltage level}$$
4. $$\text{Negative voltage}$$
Show me the answer
**Answer:** 2. $$\text{Higher voltage level}$$
**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. $$\text{Decoder}$$
2. $$\text{Multiplexer}$$
3. $$\text{Encoder}$$
4. $$\text{Demultiplexer}$$
Show me the answer
**Answer:** 4. $$\text{Demultiplexer}$$
**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. $$\text{Decoder}$$
2. $$\text{Multiplexer}$$
3. $$\text{Encoder}$$
4. $$\text{Code converter}$$
Show me the answer
**Answer:** 1. $$\text{Decoder}$$
**Explanation:**
* A BCD-to-decimal decoder converts a BCD number into its equivalent decimal representation.