# Online Digital Electronics Test - Digital Electronics Test 3

Instruction:

• This is a FREE online test. DO NOT pay money to anyone to attend this test.
• Total number of questions : 20.
• Time alloted : 30 minutes.
• Each question carry 1 mark, no negative marks.
• DO NOT refresh the page.
• All the best :-).

1.

Convert the Gray code 1011 to binary.

A.
 1011
B.
 1010
C.
 0100
D.
 1101

2.

A binary number can be converted to a decimal number by summing the decimal values of the weights of all the 1s in the binary number.

A.
 True
B.
 False

3.

1210 = 11012 = C16 = 00010010 BCD

A.
 True
B.
 False

4.

A 4-variable AND-OR circuit produces a 1 at its Y output. Which combination of inputs is correct?

A.
 A = 0, B = 0, C = 0, D = 0
B.
 A = 0, B = 1, C = 1, D = 0
C.
 A = 1, B = 1, C = 0, D = 0
D.
 A = 1, B = 0, C = 0, D = 0

5.

The expression can be directly implemented using only ________.

A.
 an XOR gate
B.
 an XNOR gate
C.
 an AOI circuit
D.
 three 2-input NAND gates

6.

The pulse width of a one-shot circuit is determined by ________.

A.
 a resistor and capacitor
B.
 two resistors
C.
 two capacitors
D.
 none of the above

7.

Synchronous binary counters can only be used for the application of timing of digital systems.

A.
 True
B.
 False

8.

An OR gate with inverted inputs functions as:

A.
 an AND gate.
B.
 a NAND gate.
C.
 a NOR gate.
D.
 an inverter.

9.

How many BCD adders would be required to add the numbers 97310 + 3910?

A.
 3
B.
 4
C.
 5
D.
 6

10.

Subtract the following binary numbers.
 0101 1000 1010 0011 1101 1110 –0010 0011 –0011 1000 –0101 0111

A.
 0011  0100    0110  1010    1000  0110
B.
 0011  0101    0110  1011    1000  0111
C.
 0011  0101    0110  1010    1000  0111
D.
 0011  0101    0110  1010    1000  0110

11.

Inside a computer all arithmetic operations take place in the ________.

A.
 accumulator register
B.
 ALU
C.
 CPU
D.
 B register

12.

The major advantage of CMOS logic circuits over TTL is very low power consumption.

A.
 True
B.
 False

13.

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

14.

The 74139 dual four-line demultiplexer functions as a decoder if ________.

A.
 the line is grounded
B.
 data input is on the line
C.
 data input is on the A0 line
D.
 the A0 line is grounded

15.

In HDL, the operation of the DEMUX is exactly described using a ________.

A.
 function
B.
 process
C.
 variable type
D.
 number of conditional signal assignment statements

16.

In the keypad encoder, just after the 4 ms mark, the simulation initiates the release of the key by changing the column value to ________, which causes the d output to go into its Hi-Z state.

A.
 0 hex
B.
 4 hex
C.
 8 hex
D.
 F hex

17.

Determine the output voltage Vout for the circuit in the given figure.

A.
 –0.5 V
B.
 0 V
C.
 +5 V
D.
 +4.3 V

18.

What is a disadvantage of CMOS in place of TTL?

A.
 It switches slower.
B.
 It uses less power.
C.
 It is smaller.
D.
 cost

19.

Show from the truth table how an exclusive-OR gate can be used to invert the data on one input if the other input is a special control function.

A.
 Using A as the control, when A = 0, X is the same as B. When A = 1, X is the same as B.
B.
 Using A as the control, when A = 0, X is the same as B. When A = 1, X is the inverse of B.
C.
 Using A as the control, when A = 0, X is the inverse of B. When A = 1, X is the same as B.
D.
 Using A as the control, when A = 0, X is the inverse of B. When A = 1, X is the inverse of B.

20.

The RST pin requires a HIGH to reset the 8051 microcontroller.

A.
 True
B.
 False