Q.1 The
NAND gate output will be low if the two inputs
are
The
(Conversion from Decimal number to
(Conversion
Ans:
A ring counter consisting of Five
15 ns because in synchronous counter all the flipflops change state
Ans:
Ans:
Ans:
Ans:
Ans:
Ans:
Ans:
Ans:
NAND gate output will be low if the two inputs
are
(A) 00
(B) 01
(B) 01
(C) 10
(D) 11
(D) 11
Ans: D
The NAND gate output will be low if the two
inputs are 11 (The Truth Table of NAND gate is shown in Table.1.1)
inputs are 11 (The Truth Table of NAND gate is shown in Table.1.1)
X(Input)

Y(Input)

F(Output)

0

0

1

0

1

1

1

0

1

1

1

0

Table 1.1 Truth Table for NAND Gate
Q.2 What
is the binary equivalent of the decimal number
368
(A) 101110000
(B) 110110000
(B) 110110000
(C) 111010000
(D) 111100000
(D) 111100000
Ans: A
The
Binary equivalent of the Decimal number 368 is 101110000
(Conversion from Decimal number to
Binary number is given in Table 1.2)
2

368

2

184 — 0

2

92
— 0 
2

46
— 0 
2

23
— 0 
2

11
— 1 
2

5
— 1 
2

2
— 1 
2

1
— 0 
0
— 1 
Table 1.2 Conversion from Decimal number to Binary number
Q.3
Q3.The decimal equivalent of hex number 1A53 is
Q3.The decimal equivalent of hex number 1A53 is
(A) 6793 (B) 6739
(C) 6973 (D) 6379
Ans: B
The decimal equivalent of Hex Number 1A53 is 6739
(Conversion
from Hex Number to Decimal Number is given below)
1

A

5

3

Hexadecimal

16³

16²

16¹

16°

Weights

(1A53)16 = (1X16³) + (10 X 16²) + (5 X 16¹) + (3 X 16º)
= 4096 + 2560 + 80 + 3
= 6739
Q.4 (734)8 = ( )16
(A) C 1 D (B) D C 1
(C) 1 C D (D) 1 D C
Ans:
D
(734)8 = (1 D C)16
0001  1101  1100
1 D
Q.5 The number of control lines for a 8 – to – 1 multiplexer is
(A) 2 (B) 3
(C) 4 (D) 5
Ans: B
The number of control lines for an 8 to 1 Multiplexer is 3
(The control signals are used to steer any one of the 8 inputs to the
output)
output)
Q.6 How many FlipFlops are required for mod–16 counter?
(A) 5 (B) 6
(C) 3 (D) 4
Ans: D
The number of flipflops is required for Mod16 Counter is 4.
(For Modm Counter, we need N
flipflops where N is chosen to be the smallest number for which 2N is greater
than or equal to m. In this case 24
greater than or equal to 1)
flipflops where N is chosen to be the smallest number for which 2N is greater
than or equal to m. In this case 24
greater than or equal to 1)
Q.7
EPROM contents can be erased by exposing
it to
EPROM contents can be erased by exposing
it to
(A)
Ultraviolet rays. (B) Infrared rays.
Ultraviolet rays. (B) Infrared rays.
(C) Burst of microwaves. (D) Intense heat radiations.
Ans: A
EPROM contents can be erased by exposing it to Ultraviolet rays
(The Ultraviolet light passes
through a window in the IC package to the EPROM chip where it releases stored
charges. Thus the stored contents are
erased).
through a window in the IC package to the EPROM chip where it releases stored
charges. Thus the stored contents are
erased).
Q.8 The hexadecimal number ‘A0’ has the decimal value equivalent to
(A) 80 (B) 256
(C) 100 (D) 160
Ans: D
The hexadecimal number
‘A0’ has the decimal value equivalent to 160
( A 0
‘A0’ has the decimal value equivalent to 160
( A 0
161 160 = 10X161 + 0X160 = 160
Q.1
Q.9 The output of a logic gate is 1 when all its inputs are at logic 0. the gate is either
(A)
a NAND or an EXOR (B) an OR or an EXNOR
a NAND or an EXOR (B) an OR or an EXNOR
(C) an
AND or an EXOR (D) a NOR or an EXNOR
AND or an EXOR (D) a NOR or an EXNOR
Ans: D
The output of a logic gate is 1 when all inputs are at logic 0. The
gate is either a NOR or an EXNOR .
gate is either a NOR or an EXNOR .
Q.14
Data can be changed from special code to temporal code by using
Data can be changed from special code to temporal code by using
(A)
Shift registers (B) counters
Shift registers (B) counters
(C) Combinational circuits (D) A/D converters.
Ans: A
Data can be changed from special code to temporal
code by using Shift Registers.
(A Register in which data gets shifted towards left or right when clock pulses
are applied is known as a Shift Register.)
code by using Shift Registers.
(A Register in which data gets shifted towards left or right when clock pulses
are applied is known as a Shift Register.)
Q.15
A ring counter consisting of five FlipFlops will have
A ring counter consisting of five FlipFlops will have
(A)
5 states (B) 10
states
5 states (B) 10
states
(C) 32 states (D) Infinite states.
Ans: A
A ring counter consisting of Five
FlipFlops will have 5 states.
Q.16
The speed of conversion is maximum in
The speed of conversion is maximum in
(A)
Successiveapproximation A/D converter.
Successiveapproximation A/D converter.
(B)
Parallelcomparative A/D converter.
Parallelcomparative A/D converter.
(C)
Counter ramp A/D converter.
Counter ramp A/D converter.
(D)
Dualslope A/D converter.
Dualslope A/D converter.
Ans: B
The speed of conversion is maximum in Parallelcomparator A/D
converter
converter
(Speed of
conversion is maximum because the comparisons of the input voltage are carried
out simultaneously.)
conversion is maximum because the comparisons of the input voltage are carried
out simultaneously.)
Q.17
The 2’s complement of the number 1101101 is
The 2’s complement of the number 1101101 is
(A) 0101110 (B) 0111110
(C) 0110010 (D) 0010011
Ans: D
The 2’s complement of the number 1101101 is 0010011 (1’s complement of
the number 1101101 is 0010010
the number 1101101 is 0010010
2’s complement of the number
1101101is 0010010 + 1 =0010011)
1101101is 0010010 + 1 =0010011)
Q.18
The correction to be applied
in decimal adder to the generated sum is
The correction to be applied
in decimal adder to the generated sum is
(A) 00101 (B) 00110
(C) 01101 (D) 01010
Ans: B
The correction to be applied in decimal
adder to the generated sum is 00110.
adder to the generated sum is 00110.
When the four
bit sum is more than 9 then the sum is invalid. In such cases, add
+6(i.e. 0110) to the four bit sum to
skip the six invalid states. If a carry is generated when adding 6, add the
carry to the next four bit group .
bit sum is more than 9 then the sum is invalid. In such cases, add
+6(i.e. 0110) to the four bit sum to
skip the six invalid states. If a carry is generated when adding 6, add the
carry to the next four bit group .
Q.19
When simplified with Boolean Algebra (x + y)(x + z) simplifies to
When simplified with Boolean Algebra (x + y)(x + z) simplifies to
(A)
x (B) x + x(y + z)
x (B) x + x(y + z)
(C) x(1 + yz) (D) x + yz
Ans: D
When simplified with Boolean Algebra (x + y)(x + z) simplifies to x +
yz [(x + y) (x + z)] = xx + xz + xy + yz
= x + xz + xy + yz ( xx = x)
yz [(x + y) (x + z)] = xx + xz + xy + yz
= x + xz + xy + yz ( xx = x)
= x(1+z) + xy + yz = x + xy +
yz { (1+z) = 1}
yz { (1+z) = 1}
= x(1 + y) + yz = x + yz { (1+y) = 1}]
Q.20
The gates required to build a half adder are
The gates required to build a half adder are
(A)
EXOR gate and NOR gate (B) EXOR gate and OR gate
EXOR gate and NOR gate (B) EXOR gate and OR gate
(C) EXOR
gate and AND gate (D) Four NAND gates.
gate and AND gate (D) Four NAND gates.
Ans: C
The gates required to build a half adder are EXOR gate and AND gate
Q.21 The code where
all successive numbers
differ from their
preceding number by single bit is
all successive numbers
differ from their
preceding number by single bit is
(A)
Binary code. (B) BCD.
Binary code. (B) BCD.
(C) Excess – 3. (D) Gray.
Ans: D
The code where all successive numbers
differ from their preceding number by single bit is Gray Code.
differ from their preceding number by single bit is Gray Code.
(It is an unweighted code. The most
important characteristic of this code is that only a single bit change occurs
when going from one code number to next.)
important characteristic of this code is that only a single bit change occurs
when going from one code number to next.)
Q.22 Which of the following is the
fastest logic
fastest logic
(A)
TTL (B) ECL
TTL (B) ECL
(C) CMOS (D) LSI
Ans: B
ECL is the fastest logic family of all
logic families.
logic families.
(High speeds
are possible in ECL because the transistors are used in difference amplifier configuration, in which they are
never driven into saturation and thereby the storage time is eliminated.
are possible in ECL because the transistors are used in difference amplifier configuration, in which they are
never driven into saturation and thereby the storage time is eliminated.
Q.23 If the input to Tflipflop is 100 Hz signal, the final output of the
three Tflipflops in cascade is
three Tflipflops in cascade is
(A) 1000 Hz (B) 500 Hz
(C) 333 Hz (D) 12.5 Hz.
Ans: D
If the input to Tflipflop is 100 Hz signal,
the final output
of the three
T flipflops in cascade is 12.5 Hz
the final output
of the three
T flipflops in cascade is 12.5 Hz
Q.24 Which of the memory is volatile memory
(A)
ROM (B) RAM
ROM (B) RAM
(C) PROM (D) EEPROM
Ans: B
RAM is a volatile memory (Volatile
memory means the contents of the RAM get erased as soon as the power
goes off.)
memory means the contents of the RAM get erased as soon as the power
goes off.)
Q.25

8 is equal to signed binary number



(A) 10001000

(B) 00001000


(C) 10000000

(D) 11000000

Ans: A
– 8 is equal to signed binary number 10001000
Q.26
DeMorgan’s first theorem shows the equivalence of
DeMorgan’s first theorem shows the equivalence of
(A) OR gate and Exclusive OR gate.
(B)
NOR gate and Bubbled AND gate.
NOR gate and Bubbled AND gate.
(C) NOR gate and NAND gate.
(D) NAND gate and NOT gate
Ans: B
DeMorgan’s first theorem shows
the equivalence of NOR gate and Bubbled AND gate
the equivalence of NOR gate and Bubbled AND gate
Q.27
The digital logic family which has the lowest propagation delay time is
The digital logic family which has the lowest propagation delay time is
(A)
ECL (B) TTL
ECL (B) TTL
(C) CMOS (D) PMOS
Ans: A
The digital logic family which has the lowest propagation delay time
is ECL
is ECL
(Lowest
propagation delay time is possible in ECL because the transistors are used in
difference amplifier configuration, in which they are never driven into
saturation and thereby the storage time is eliminated).
propagation delay time is possible in ECL because the transistors are used in
difference amplifier configuration, in which they are never driven into
saturation and thereby the storage time is eliminated).
Q.28
The device which changes from serial data to parallel data is
The device which changes from serial data to parallel data is
(A) COUNTER (B) MULTIPLEXER
(C) DEMULTIPLEXER (D) FLIPFLOP
Ans: C
The device which changes from serial data to parallel data is
demultiplexer.
demultiplexer.
(A demultiplexer takes in data
from one line and directs it to any of its N outputs depending on the status of
the select inputs.)
from one line and directs it to any of its N outputs depending on the status of
the select inputs.)
Q.29
A device which converts BCD to Seven Segment is called
A device which converts BCD to Seven Segment is called
(A)
Encoder (B) Decoder
Encoder (B) Decoder
(C) Multiplexer (D) Demultiplexer
Ans: B
A device which converts BCD to Seven
Segment is called DECODER.
Segment is called DECODER.
(A decoder coverts binary words into alphanumeric
characters.)
characters.)
Q.30
In a JK FlipFlop, toggle means
In a JK FlipFlop, toggle means
(A) Set Q = 1 and Q = 0.
(B)
Set Q = 0 and Q = 1.
Set Q = 0 and Q = 1.
(C) Change the output to the
opposite state.
opposite state.
(D) No change in output.
Ans: C
In a JK FlipFlop, toggle means Change the output to the opposite
state.
Q.31 The access time of ROM using bipolar transistors is about
(A)
1 sec (B) 1 msec
1 sec (B) 1 msec
(C) 1 µsec (D) 1 nsec.
Ans: C
The access time of ROM using bipolar transistors is about 1 m sec.
Q.32
The A/D converter
whose conversion time is independent of the number
of bits is
The A/D converter
whose conversion time is independent of the number
of bits is
(A) Dual slope (B) Counter type
(C) Parallel conversion (D) Successive approximation.
Ans: C
The A/D converter whose conversion time is independent of the Number
of bits is Parallel conversion.
of bits is Parallel conversion.
(This type uses an array of comparators connected in parallel and
comparators compare the input voltage at a particular ratio of the reference
voltage).
comparators compare the input voltage at a particular ratio of the reference
voltage).
Q.3When signed numbers are used in binary arithmetic, then which one of
the following notations would have unique representation for zero.
the following notations would have unique representation for zero.
(A) Signmagnitude. (B) 1’s complement.
(C) 2’s complement. (D) 9’s complement.
Ans: A
Q.38 A 4bit synchronous counter uses flipflops with propagation delay
times of 15 ns each. The maximum possible time required for change of state
will be
times of 15 ns each. The maximum possible time required for change of state
will be
(A) 15 ns. (B) 30 ns.
(C) 45 ns. (D) 60 ns.
Ans: A
15 ns because in synchronous counter all the flipflops change state
at the same time.
Q.39 Words having 8bits are to be stored into computer memory. The number
of lines required for writing into memory are
of lines required for writing into memory are
(A) 1. (B) 2.
(C) 4. (D) 8.
Ans: D
Because 8bit words required 8
bit data lines.
bit data lines.
Q.40 In successiveapproximation A/D converter, offset
voltage equal to D/A converter’s
output. This is done to
voltage equal to D/A converter’s
output. This is done to
(A) Improve the speed of operation.
(B)
Reduce the maximum quantization error.
Reduce the maximum quantization error.
(C)
Increase the number of bits at the
output.
Increase the number of bits at the
output.
(D)
Increase the range of input voltage that can be converted.
Increase the range of input voltage that can be converted.
Ans: B
Q.41
The decimal equivalent of Binary number 11010 is
The decimal equivalent of Binary number 11010 is
(A) 26. (B) 36.
(C) 16. (D) 23.
Ans: A
11010 = 1 X 24 + 1 X 2 3 + 0 X 22 + 1 X 21 = 26
1 LSB
is added to the 2
is added to the 2
Q.42
1’s complement representation of decimal number
of 17 by using
8 bit representation is
1’s complement representation of decimal number
of 17 by using
8 bit representation is
(A) 1110 1110 (B) 1101 1101
(C) 1100 1100 (D) 0001 0001
Ans: A
(17)10
= (10001)2
= (10001)2
In 8 bit = 00010001
1’s Complement = 11101110
Q.43 The excess 3 code of decimal number 26
is
is
(A) 0100 1001 (B) 01011001
(C) 1000 1001 (D) 01001101
Ans: B
(26)10
in BCD is ( 00100110 ) BCD
in BCD is ( 00100110 ) BCD
Add 011 to each BCD 01011001 for excess – 3
Q.44 How many AND gates are required to realize Y = CD+EF+G
(A) 4 (B) 5
(C) 3 (D) 2
Ans: D
To realize Y = CD + EF + G
Two AND gates are required (for CD & EF).
Q.45 How many select lines will a 16 to 1 multiplexer will have
(A) 4 (B) 3
(C) 5 (D) 1
Ans: A
In 16 to 1 MUX four select
lines will be required to select 16 ( 24 ) inputs.
lines will be required to select 16 ( 24 ) inputs.
Q.46 How many flip flops are required to construct a decade counter
(A) 10 (B) 3
(C) 4 (D) 2
Ans: C
Decade counter counts 10 states from 0 to 9 ( i.e. from 0000 to 1001 )Thus four FlipFlop’s are required.
Q.47 Which TTL logic gate is used for wired
ANDing
(A)
Open collector output (B) Totem Pole
Open collector output (B) Totem Pole
(C) Tri state output (D) ECL gates
Ans: A
Open collector output.
Q.48

CMOS circuits consume power



(A) Equal to TTL

(B) Less than TTL


(C) Twice of TTL

(D) Thrice of TTL

Ans: B
As in CMOS one device is ON & one is Always OFF so power
consumption is low.
consumption is low.
Q.49
In a RAM, information can be stored
In a RAM, information can be stored
(A)
By the user, number of times.
By the user, number of times.
(B)
By the user, only once.
By the user, only once.
(C)
By the manufacturer, a number of times.
By the manufacturer, a number of times.
(D)
By the manufacturer only once.
By the manufacturer only once.
Ans: A
RAM is used by the user, number of times.
Q.52 The chief reason
why digital computers
use complemented subtraction is that it
(A)
Simplifies the circuitry.
Simplifies the circuitry.
(B)
Is a very simple process.
Is a very simple process.
(C)
Can handle negative numbers easily.
Can handle negative numbers easily.
(D)
Avoids direct subtraction
Avoids direct subtraction
Ans:
C
Using complement method negative numbers can also be subtracted.
Q.53
In a positive logic system, logic state 1 corresponds to
In a positive logic system, logic state 1 corresponds to
(A)
positive voltage (B) higher voltage level
positive voltage (B) higher voltage level
(C) zero voltage level (D) lower
voltage level
voltage level
Ans: B
We decide two
voltages levels for positive digital logic. Higher voltage represents logic 1
& a lower voltage represents logic 0.
voltages levels for positive digital logic. Higher voltage represents logic 1
& a lower voltage represents logic 0.
Q.54 The commercially available 8input multiplexer integrated circuit in the TTL family
is
is
(A) 7495. (B) 74153.
(C) 74154. (D) 74151.
Ans: B
MUX integrated circuit in TTL is 74153.
Q.55 CMOS circuits are extensively used for ONchip
computers mainly because
of their extremely
computers mainly because
of their extremely
(A)
low power dissipation. (B) high noise immunity.
low power dissipation. (B) high noise immunity.
(C) large packing density. (D) low cost.
Ans: C
Because CMOS circuits have large packing density.
Q.56
The MSI chip 7474 is
The MSI chip 7474 is
(A)
Dual edge triggered JK flipflop (TTL).
Dual edge triggered JK flipflop (TTL).
(B)
Dual edge triggered D flipflop (CMOS).
Dual edge triggered D flipflop (CMOS).
(C)
Dual edge triggered D flipflop (TTL).
Dual edge triggered D flipflop (TTL).
(D)
Dual edge triggered JK flipflop (CMOS).
Dual edge triggered JK flipflop (CMOS).
Ans: C
MSI chip 7474 dual edge triggered D FlipFlop.
Q.57
Which of the following memories stores the most number of bits
Which of the following memories stores the most number of bits
(A) a 5M´ 8 memory. (B) a
1M ´ 16 memory.
1M ´ 16 memory.
(C) a 5M ´ 4 memory. (D) a
1M ´12 memory.
1M ´12 memory.
Ans:
A
5Mx8 = 5 x 220 x 8 = 40M (max)
Q.58
The process of entering data into a ROM is called
The process of entering data into a ROM is called
(A)
burning in the ROM (B) programming the ROM
burning in the ROM (B) programming the ROM
(C) changing the ROM (D) charging the ROM
Ans: B
The process of entering data into ROM is known as programming the ROM.
Q.59
When the set of input data to an even parity generator is 0111, the output will be
When the set of input data to an even parity generator is 0111, the output will be
(A) 1 (B) 0
(C) Unpredictable (D) Depends on the previous input
Ans:
B
In even parity generator if
number of 1 is odd then output will be zero.
number of 1 is odd then output will be zero.
Q.60
The number 140 in octal is equivalent
to
The number 140 in octal is equivalent
to
(A) (96)10 . (B) (86)10 .
(C) (90)10 . (D) none of these.
Ans: A
(140)8 = (96)10
1 x 82 + 4 x 8 + 0x 1 = 64
+ 32 = 96
+ 32 = 96
Q.61
The NOR gate output will be low if the two inputs are
The NOR gate output will be low if the two inputs are
(A) 00 (B) 01
(C) 10 (D) 11
Ans: B, C, or D
O/P is low if any of the I/P is high
Q.62
Which of the following is the fastest
logic?
Which of the following is the fastest
logic?
(A) ECL (B) TTL
(C) CMOS (D) LSI
Ans: A
Q.63
How many flipflops are
required to construct mod 30 counter
How many flipflops are
required to construct mod 30 counter
(A) 5 (B) 6
(C) 4 (D) 8
Ans:
A
Mod – 30 counter +/ needs 5 FlipFlop as 30 < 25 Mod – N counter counts total ‘ N ‘ number of
states.
states.
To count ‘N’ distinguished states we need
minimum n FlipFlop’s as [N = 2n] For eg. Mod
8 counter requires 3 FlipFlop’s (8 = 23)
minimum n FlipFlop’s as [N = 2n] For eg. Mod
8 counter requires 3 FlipFlop’s (8 = 23)
Q.64 How many address bits are required to represent a 32 K memory
(A)
10 bits. (B) 12 bits.
10 bits. (B) 12 bits.
(C) 14 bits. (D) 16 bits.
Ans:
D
32K = 25 x 210 = 215,
Thus 15 address bits are required, Only 16 bits can address it.
Q.65 The number of control lines for 16 to 1 multiplexer is
(A) 2. (B) 4.
(C) 3. (D) 5.
Ans:
B
As 16 = 24, 4 Select lines are
required.
required.
Q.66 Which of following requires refreshing?
(A)
SRAM. (B) DRAM.
SRAM. (B) DRAM.
(C) ROM. (D) EPROM.
Ans: B
Q.67 Shifting a register
content to left by one bit position
is equivalent to
content to left by one bit position
is equivalent to
(A)
division by two. (B) addition by two.
division by two. (B) addition by two.
(C) multiplication by two. (D) subtraction by two.
Ans:C
Q.68
For JK flip flop with J=1, K=0, the output
after clock pulse will be
For JK flip flop with J=1, K=0, the output
after clock pulse will be
(A) 0. (B) 1.
(C) high impedance. (D) no change.
Ans: B
Q.69
Convert decimal 153 to octal.
Equivalent in octal will be
Convert decimal 153 to octal.
Equivalent in octal will be
(A) (231)8 . (B) (331)8 .
(C) (431)8 . (D) none of these.
Ans: A
Q.70
The decimal equivalent of (1100)2 is
The decimal equivalent of (1100)2 is
(A) 12 (B) 16
(C) 18 (D) 20
Ans: A
(1100)2 = (12)10
Q.71
The binary equivalent of (FA)16 is
The binary equivalent of (FA)16 is
(A) 1010 1111 (B) 1111 1010
(C) 10110011 (D) none
of these
of these
Ans: B
(FA)16 = (11111010)10
Q.72
The output of SR flip flop when S=1, R=0 is
The output of SR flip flop when S=1, R=0 is
(A) 1 (B) 0
(C) No change (D) High impedance
Ans: A
As for the SR flipflop S=set input R=reset input ,when S=1, R=0,
Flipflop will be set.
Flipflop will be set.
Q.73
The number of flip flops contained in IC 7490 is
The number of flip flops contained in IC 7490 is
(A) 2. (B) 3.
(C) 4. (D) 10.
Ans: A
Q.74
The number of control lines for 32 to 1 multiplexer is
The number of control lines for 32 to 1 multiplexer is
(A) 4. (B) 5.
(C) 16. (D) 6.
Ans: B
The number of control lines for 32 (25)
and to select one input among them total 5 select lines are required.
and to select one input among them total 5 select lines are required.
Q.75
How many twoinput
AND and OR gates are required to realize Y=CD+EF+G
How many twoinput
AND and OR gates are required to realize Y=CD+EF+G
(A) 2,2. (B) 2,3.
(C) 3,3. (D) none
of these.
of these.
Ans: A
Y=CD+EF+G
Number of two input AND gates=2
Number of two input OR gates = 2
Number of two input OR gates = 2
One OR gate to OR CD and EF and next to OR of G & output of first
OR gate.
OR gate.
Q.76
Which of following can not be accessed
randomly
Which of following can not be accessed
randomly
(A)
DRAM. (B) SRAM.
DRAM. (B) SRAM.
(C) ROM. (D) Magnetic tape.
Ans: D
Magnetic tape can only be accessed sequentially.
Q.77
The excess3 code of decimal 7 is represented by
The excess3 code of decimal 7 is represented by
(A) 1100. (B) 1001.
(C) 1011. (D) 1010.
Ans: D
An excess 3 code is always equal to the binary code +3
Q.78
When an input signal A=11001
is applied to a NOT gate serially, its output signal is
When an input signal A=11001
is applied to a NOT gate serially, its output signal is
(A) 00111. (B) 00110.
(C) 10101. (D) 11001.
Ans: B
As A=11001 is serially applied to a NOT gate, first input applied will
be LSB 00110.
be LSB 00110.
Q.79
The result of adding hexadecimal number A6 to 3A is
The result of adding hexadecimal number A6 to 3A is
(A)
DD. (B) E0.
DD. (B) E0.
(C) F0. (D) EF.
Ans: B
Q.80
A universal logic gate is one, which can be used to generate any logic
function. Which of the following is a universal logic gate?
A universal logic gate is one, which can be used to generate any logic
function. Which of the following is a universal logic gate?
(A) OR (B) AND
(C) XOR (D) NAND
Ans: D
NAND can generate any logic function.
Q.81
The logic 0 level of a CMOS logic device is approximately
The logic 0 level of a CMOS logic device is approximately
(A)
1.2 volts (B) 0.4 volts
1.2 volts (B) 0.4 volts
(C) 5 volts (D) 0 volts
Ans: D
CMOS logic low level is 0 volts approx.
Q.82
Karnaugh map is used for the purpose
of
Karnaugh map is used for the purpose
of
(A)
Reducing the electronic circuits used.
Reducing the electronic circuits used.
(B)
To map the given Boolean logic function.
To map the given Boolean logic function.
(C)
To minimize the terms in a Boolean expression.
To minimize the terms in a Boolean expression.
(D)
To maximize the terms of a given a Boolean expression.
To maximize the terms of a given a Boolean expression.
Ans: C
Q.83
A full adder logic circuit will have
A full adder logic circuit will have
(A)
Two inputs and one output.
Two inputs and one output.
(B)
Three inputs and three outputs.
Three inputs and three outputs.
(C)
Two inputs and two outputs.
Two inputs and two outputs.
(D)
Three inputs and two outputs.
Three inputs and two outputs.
Ans:
D
A full adder
circuit will add two bits and it will also accounts the carry input generated
in the previous stage. Thus three inputs and two outputs (Sum and Carry) are
there.
circuit will add two bits and it will also accounts the carry input generated
in the previous stage. Thus three inputs and two outputs (Sum and Carry) are
there.
Q.84
An eight stage ripple counter uses a flipflop with propagation delay
of 75 nanoseconds. The pulse width of the strobe is 50ns. The frequency of the
input signal which can be used for proper operation of the counter is approximately
An eight stage ripple counter uses a flipflop with propagation delay
of 75 nanoseconds. The pulse width of the strobe is 50ns. The frequency of the
input signal which can be used for proper operation of the counter is approximately
(A) 1 MHz. (B) 500 MHz.
(C) 2 MHz. (D) 4 MHz.
Ans: A
Maximum time taken for all
flipflops to stabilize is 75ns x 8 + 50 = 650ns. Frequency of operation must
be less than 1/650ns = 1.5 MHz.
flipflops to stabilize is 75ns x 8 + 50 = 650ns. Frequency of operation must
be less than 1/650ns = 1.5 MHz.
Q.85
The output of a JK flipflop with asynchronous preset and clear inputs
is ‘1’. The output can be changed to ‘0’ with one of the following conditions.
The output of a JK flipflop with asynchronous preset and clear inputs
is ‘1’. The output can be changed to ‘0’ with one of the following conditions.
(A) By applying J = 0, K = 0 and
using a clock.
using a clock.
(B)
By applying J = 1, K = 0 and using the
clock.
By applying J = 1, K = 0 and using the
clock.
(C)
By applying J = 1, K = 1 and using the
clock.
By applying J = 1, K = 1 and using the
clock.
(D)
By applying a synchronous preset input.
By applying a synchronous preset input.
Ans: C
Preset state of JK FlipFlop =1
With J=1 K=1 and the clock next
state will be complement of the present state.
state will be complement of the present state.
Q.86
The information in ROM is stored
The information in ROM is stored
(A)
By the user any number of times.
By the user any number of times.
(B)
By the manufacturer during fabrication of the device.
By the manufacturer during fabrication of the device.
(C)
By the user using ultraviolet light.
By the user using ultraviolet light.
(D)
By the user once and only once.
By the user once and only once.
Ans: B
Q.87
The conversation speed of an analog to digital converter is maximum
with the following technique.
The conversation speed of an analog to digital converter is maximum
with the following technique.
(A) Dual slope AD converter.
(B)
Serial comparator AD converter.
Serial comparator AD converter.
(C)
Successive approximation AD converter.
Successive approximation AD converter.
(D)
Parallel comparator AD converter.
Parallel comparator AD converter.
Ans: D
Q.88
A weighted resistor
digital to analog converter using N bits requires a total of
A weighted resistor
digital to analog converter using N bits requires a total of
(A) N precision resistors. (B) 2N precision resistors.
(C) N + 1 precision resistors. (D) N – 1 precision resistors.
Ans: A
Q.89
The 2’s complement of the number 1101110 is
The 2’s complement of the number 1101110 is
(A) 0010001. (B) 0010001.
(C) 0010010. (D) None.
Ans: C
1’s complement of 1101110 is = 0010001
Thus 2’s complement of 1101110 is = 0010001 + 1 = 0010010
Q.90
The decimal equivalent of Binary number 10101 is
The decimal equivalent of Binary number 10101 is
(A) 21 (B) 31
(C) 26 (D) 28
Ans:
A
1×24 + 0x23 +1×22 +0x21 + 1×20
= 16 + 0 + 4 + 0 + 1 = 21.
Q.91
How many two input AND gates and two input OR gates
are required to realize
Y = BD+CE+AB
How many two input AND gates and two input OR gates
are required to realize
Y = BD+CE+AB
(A) 1, 1 (B) 4, 2
(C) 3, 2 (D) 2, 3
Ans: A
There are three product terms, so three AND gates of two inputs are
required.
required.
As only two input OR gates are
available, so two OR gates are required to get the logical sum of three product
terms.
available, so two OR gates are required to get the logical sum of three product
terms.
Q.92
How many select lines will a 32:1 multiplexer will have
How many select lines will a 32:1 multiplexer will have
(A) 5. (B) 8.
(C) 9. (D) 11.
Ans: A
For 32 inputs, 5 select lines will be required, as 25 = 32.
Q.93
How many address bits are required to represent 4K memory
How many address bits are required to represent 4K memory
(A)
5 bits. (B) 12 bits.
5 bits. (B) 12 bits.
(C) 8 bits. (D) 10 bits.
Ans: B
For representing 4K
memory, 12 address bits are required as
4K = 22 x
210 = 212 (1K = 1024 = 210)
memory, 12 address bits are required as
4K = 22 x
210 = 212 (1K = 1024 = 210)
Q.94
For JK flipflop J = 0, K=1, the output after clock pulse will be
For JK flipflop J = 0, K=1, the output after clock pulse will be
(A)
1. (B) no change.
1. (B) no change.
(C) 0. (D) high impedance.
Ans: C
J=0, K=1, these inputs will reset the flipflop after the clock pulse.
So whatever be the previous output, the next state will be 0.
So whatever be the previous output, the next state will be 0.
Q.95
Which of following are known as universal gates
Which of following are known as universal gates
(A)
NAND & NOR. (B) AND & OR.
NAND & NOR. (B) AND & OR.
(C) XOR & OR. (D) None.
Ans: A
NAND & NOR are known as universal gates, because any digital
circuit can be realized completely by using either of these two gates.
circuit can be realized completely by using either of these two gates.
Q.96
Which of the following memories
stores the most number of bits
Which of the following memories
stores the most number of bits
(A) 64K ´ 8 memory. (B) 1M
´ 8 memory.
´ 8 memory.
(C) 32M
´ 8 memory. (D) 64 ´ 6 memory.
´ 8 memory. (D) 64 ´ 6 memory.
Ans: C
32M x 8 stores most number of bits
25 x 220 = 225 (1M = 220 = 1K x 1K = 210 x 210)
Q.97
Which of following consume minimum
power
Which of following consume minimum
power
(A)
TTL. (B) CMOS.
TTL. (B) CMOS.
(C) DTL. (D) RTL.
Ans: B
CMOS consumes minimum power as in CMOS one pMOS & one nMOS
transistors are connected in complimentary mode, such that one device
is ON & one is OFF.
transistors are connected in complimentary mode, such that one device
is ON & one is OFF.
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