Question 1

An 8 bit DAC has a full scale output of 2 mA and full scale error of ± 0.5%. If input is 10000000 the range of outputs is

Accepted Answer

10000000 = 128, 11111111 = 255 If there is no error, output = = 1004μA. Maximum error = Hence range of output 994 to 1014 μA.

Question 2

The expression Y = pM (0, 1, 3, 4) is

Accepted Answer

This is product of sums expression.

Question 3

For the K map in the given figure the simplified Boolean expression is

Accepted Answer

Question 4

The number of distinct Boolean expression of 4 variables is

Accepted Answer

22n = 224 = 216 .

Question 5

For the truth table of the given figure Y =

Accepted Answer

Y = A B C + A B C + AB C + A B C = A B (C + C) + A B (C + C) = A B + AB = B(A + A) = B.

Question 6

Zero suppression is not used in actual practice.

Accepted Answer

Zero suppression is commonly used.

Question 7

If the functions w, x, y, z are as follows. w = R + PQ + RS , x = PQR S + PQR S + PQ R S Then

Accepted Answer

Use k-map, then it will be easy.

Question 8

The access time of a word in 4 MB main memory is 100 ms. The access time of a word in a 32 kb data cache memory is 10 ns. The average data cache bit ratio is 0.95. The efficiency of memory access time is

Accepted Answer

Access time = 0.95 x 10 + 0.05 x 100.

Question 9

An OR gate has 4 inputs. One input is high and the other three are low. The output

Accepted Answer

In OR any input high means high output.

Question 10

Which of the following is non-saturating?

Accepted Answer

Since it is non-saturating, ECL has low propagation delay.

Question 11

A device which converts BCD to seven segment is called

Accepted Answer

Decoder converts binary/BCD to alphanumeric.

Question 12

A 12 bit ADC is used to convert analog voltage of 0 to 10 V into digital. The resolution is

Accepted Answer

.

Question 13

In a 7 segment display, LEDs b and c lit up. The decimal number displayed is

Accepted Answer

Question 14

BCD input 1000 is fed to a 7 segment display through a BCD to 7 segment decoder/driver. The segments which will lit up are

Accepted Answer

1000 equals decimal 8 Therefore all segments will lit up.

Question 15

7BF16 = __________ 2

Accepted Answer

7BF16 = 7 x 162 + 11 x 161 + 15 x 160 = 1983 in decimal = 0111 1011 1111 in binary.

Question 16

The circuit in the given figure is

Accepted Answer

Since V(1) is lower state than V(0) it is a negative logic circuit. Since diodes are in parallel, it is an OR gate.

Question 17

In a BCD to 7 segment decoder the minimum and maximum number of outputs active at any time is

Accepted Answer

Minimum number of outputs when input is decimal 1 and maximum number of outputs when input is decimal 8.

Question 18

For the gate in the given figure the output will be

Accepted Answer

If A = 0, Y = 1 and A = 1, Y = 0 Therefore Y = A.

Question 19

AB + AB =

Accepted Answer

AB + AB = A(B + B) = A . 1 = A.

Question 20

A three state switch has three outputs. These are

Accepted Answer

Third state is floating.

Digital Electronics Questions