296 + Interview Questions in Digital Electronics in Electronics and Communication Engineering Page 5 InterviewSolution

201.	The first machine cycle of an instruction is always
Answer» Fetch cycle is always first machine cycle.

Discussion

202.	A counter has N flip flops. The total number of states are
Answer» One flip-flop means 2 states and N flip-flops means 2N states.

Discussion

203.	Out of S, R, J, K, Preset, Clear inputs to flip flops, the synchronous inputs are
Answer» Preset and clear inputs are not applied in any fixed sequence.

Discussion

204.	In a mod-12 counter the input clock frequency is 10 kHz. The output frequency is
Answer» Mod-12 counter is divide by 12 counter. Output frequency = = 0.833 kHz.

Discussion

205.	Inputs A and B of the given figure are applied to a NAND gate. The output is LOW
Answer» NAND gate gives Low output if all inputs are High. For other combinations of inputs, output is High.

Discussion

206.	AECF1 + 15ACD = __________ .
Answer» Convert to decimal, add and change the result to hexadecimal.

Discussion

207.	A XOR gate has inputs A and B and output Y. Then the output equation is
Answer» XOR gate recognises odd number of 1's.

Discussion

208.	Wired AND connection can be used in TTL with totem pole output.
Answer» F, No it cannot be used.

Discussion

209.	A X 2 __________ .
Answer» A16 = 10, 216 = 2, 10 x 2 = 20 in decimal = 14 in hexadecimal.

Discussion

210.	For the binary number 11101000, the equivalent hexadecimal number is
Answer» 11 01000 = 128 + 64 + 32 + 8 = 232 in decimal = E 8 in hexadecimal.

Discussion

211.	Boolean expression for the output of XNOR (Equivalent) logic gate with inputs A and B is
Answer» (A + B) (A + B) = A ⊕ B.

Discussion

212.	An SR flip flop can be built using NOR gates or NAND gates.
Answer»

Discussion

213.	In the given figure R = R = 1 kΩ, then V =
Answer» Transistor is off. .

Discussion

214.	A 14 pin NOT gate 1C has __________ NOT gates.
Answer» 6 Input pins, 6 output pins, 1 supply pin and 1 ground pin. Hence 6 NOT gates.

Discussion

215.	F's complement of (2BFD) is
Answer»

Discussion

216.	A Karnaugh map with 4 variables has
Answer» 24= 16.

Discussion

217.	An 8 bit data is to be entered into a parallel in register. The number of clock pulses required is
Answer» In a parallel in register only one pulse is needed to enter data.

Discussion

218.	The total number of input words for 4 input OR gate is
Answer» 24 = 16.

Discussion

219.	In digital circuits Schottky transistors are preferred over normal transistors because of their
Answer» Schottky transistors have low switching time and hence low propagation delay.

Discussion

220.	A flip flop is a
Answer» It is a memory element used in digital circuits.

Discussion

221.	A 4 bit parallel type A/D converter uses a 6 volt reference. How many comparators are required and what is the resolution in volts?
Answer» No. of comparators = 2n - 1 = 24 - 1 = 15 .

Discussion

222.	Quantization error occurs in
Answer» Analog input can have any value but digital value can have only 2N discrete levels (for N bits). Hence quantization error in A/D conversion.

Discussion

223.	A universal shift register can shift
Answer» Both left to right and right to left operations are possible in universal shift register.

Discussion

224.	Available multiplexer IC package can have a maximum of 8 inputs.
Answer» 16 : 1 1C multiplexer is also available.

Discussion

225.	For the logic circuit of the given figure the simplified Boolean equation
Answer» = (A + B) (C + D) (E + F).

Discussion

226.	A combination circuit is one in which the output depends on
Answer» Combinational circuit does not have memory.

Discussion

227.	71 = __________ .
Answer» 71 in octal = 7 x 8 + 1= 57 in decimal = 111001 in binary.

Discussion

228.	1011 x 101 = __________
Answer» 1011 = 11 in decimal and 101 = 5 in decimal, 11 X 5 = 55.

Discussion

229.	A mod 4 counter will count
Answer» Mod 4 counter has 4 states, 0 to 3.

Discussion

230.	In the given figure shows a 4 bit serial in parallel out right shift register. The initial contents as shown are 0110. After 3 clock pulses the contents will be
Answer» Output of XOR gate is input to register.

Discussion

231.	It is desired to display the digit 7 using a seven segment display. The LEDs to be turned on are
Answer»

Discussion

232.	For a MOD-12 counter, the FF has a = 60 ns The NAND gate has a of 25 n sec. The clock frequency is
Answer» For a proper working, the clock period should be equal to or greater than tpd = Mod 12 - 4FFs = 4 x 60 = 240 nsec. Total tpd = 240 + 25 = 265 nsec. = fc and fc = 3.774 MHz.

Discussion

233.	100101 is equal to decimal number
Answer» 32 + 4 + 1 = 37 in decimal.

Discussion

234.	In the figure, the LED
Answer» To emit the light, it is necessary NAND gate output is zero, for NAND O/P zero. Both the I/O must be height. And it is not possible in any case.

Discussion

235.	A 4 bit ripple counter uses flip flops with propagation delay of 50 ns each. The maximum clock frequency which can be used is
Answer» Time delay = 50 x 4 x 10-9s, .

Discussion

236.	An AND gate has two inputs A and B and one inhibit input S. Out of total 8 input states, output is 1 in
Answer» Only one input, i.e., A = 1, B = 1 and S = 0 gives output 1.

Discussion

237.	268 = __________ .
Answer» 10C in hexadecimal = 1 x 162 + 12 = 268 in decimal.

Discussion

238.	In a JK Master slave flip flop
Answer»

Discussion

239.	In a 7 segment display the segments are lit. The decimal number displayed will be
Answer»

Discussion

240.	The minimum number of comparators required to build an 8 bit flash ADC is
Answer» 2n - 1 = 28 - 1 = 255.

Discussion

241.	For a Mod-64 synchronous counter the number of flip flops and AND gates needed is
Answer» 26 = 64 Hence 6 flip-flops. The number of AND gates is 6 - 2 = 4 see in the given figure

Discussion

242.	A 4 bit DAC gives an output of 4.5 V for input of 1001. If input is 0110, the output is
Answer»

Discussion

243.	In 2's complement form, - 2 is
Answer» A = 1110, A = 0001, A + 1 = 0001 + 1 = 0010 = 2 Therefore A = -2.

Discussion

244.	The Boolean function/implemented in the figure using two I/P multiplexers is
Answer» when B = 1, f1 = ABC B = 0, f2 = ABC f = f1 + f2 = ABC + ABC.

Discussion

245.	Am equivalent 2's complement representation of the 2's complement number 1101 is
Answer» 2's complement of (1101)2 = 0011

Discussion

246.	The number of digits in hexadecimal system
Answer» It has 16 digits 0 to 15.

Discussion

247.	Which of these is the most recent display device?
Answer» VF display can operate at very low voltages, has low power consumption and very long life.

Discussion

248.	A NOR gate has 3 inputs A, B, C. For which combination of inputs is output HIGH
Answer» NOR gate gives High output when all inputs are Low.

Discussion

249.	9's complement of 56 is
Answer» 99 - 56 = 43.

Discussion

250.	4 bit 2's complement representation of a decimal number is 1000. The number is
Answer» (a) and (d) both are option, But there is meaning to represent a positive number in 2's complement form, we take complement representation for negative number only. Therefore most appropriate number is "-8".

Discussion

Explore topic-wise InterviewSolutions in .

The first machine cycle of an instruction is always

A counter has N flip flops. The total number of states are

Out of S, R, J, K, Preset, Clear inputs to flip flops, the synchronous inputs are

In a mod-12 counter the input clock frequency is 10 kHz. The output frequency is

Inputs A and B of the given figure are applied to a NAND gate. The output is LOW

AECF1 + 15ACD = __________ .

A XOR gate has inputs A and B and output Y. Then the output equation is

Wired AND connection can be used in TTL with totem pole output.

A X 2 __________ .

For the binary number 11101000, the equivalent hexadecimal number is

Boolean expression for the output of XNOR (Equivalent) logic gate with inputs A and B is

An SR flip flop can be built using NOR gates or NAND gates.

In the given figure R = R = 1 kΩ, then V =

A 14 pin NOT gate 1C has __________ NOT gates.

F's complement of (2BFD) is

A Karnaugh map with 4 variables has

An 8 bit data is to be entered into a parallel in register. The number of clock pulses required is

The total number of input words for 4 input OR gate is

In digital circuits Schottky transistors are preferred over normal transistors because of their

A flip flop is a

A 4 bit parallel type A/D converter uses a 6 volt reference. How many comparators are required and what is the resolution in volts?

Quantization error occurs in

A universal shift register can shift

Available multiplexer IC package can have a maximum of 8 inputs.

For the logic circuit of the given figure the simplified Boolean equation

A combination circuit is one in which the output depends on

71 = __________ .

1011 x 101 = __________

A mod 4 counter will count

In the given figure shows a 4 bit serial in parallel out right shift register. The initial contents as shown are 0110. After 3 clock pulses the contents will be

It is desired to display the digit 7 using a seven segment display. The LEDs to be turned on are

For a MOD-12 counter, the FF has a = 60 ns The NAND gate has a of 25 n sec. The clock frequency is

100101 is equal to decimal number

In the figure, the LED

A 4 bit ripple counter uses flip flops with propagation delay of 50 ns each. The maximum clock frequency which can be used is

An AND gate has two inputs A and B and one inhibit input S. Out of total 8 input states, output is 1 in

268 = __________ .

In a JK Master slave flip flop

In a 7 segment display the segments are lit. The decimal number displayed will be

The minimum number of comparators required to build an 8 bit flash ADC is

For a Mod-64 synchronous counter the number of flip flops and AND gates needed is

A 4 bit DAC gives an output of 4.5 V for input of 1001. If input is 0110, the output is

In 2's complement form, - 2 is

The Boolean function/implemented in the figure using two I/P multiplexers is

Am equivalent 2's complement representation of the 2's complement number 1101 is

The number of digits in hexadecimal system

Which of these is the most recent display device?

A NOR gate has 3 inputs A, B, C. For which combination of inputs is output HIGH

9's complement of 56 is

4 bit 2's complement representation of a decimal number is 1000. The number is