This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Signals”.

1. A cosine wave voltage signal has a 10V RMS value and 60Hz frequency. Also at time, t=0, the value of the voltage signal is equal to its RMS value. Which of the following is the correct mathematical representation of the voltage signal?

a) 10 cos(60t)

b) 10 cos (120πt)

c) 14.14 cos(60t + π/4)

d) 14.14 cos(120πt + π/4)

View Answer

Explanation: Only equation 14.14 cos(120πt + π/4) satisfies all the given parameters.

2. Which of the following is a characteristic of digital signal?

a) It takes quantized value

b) Its waveform is a continuous function

c) The maximum number of signals that can be produced by N bits is 2^{N-1}

d) There is no loss of value after converting an analog signal to digital signal

View Answer

Explanation: Digital signal is non continuous and has discrete sets of possible value which it can take.

3. Consider an N-bits ADC (Analog to Digital Converter) whose analog input varies from 0 to Vmax, then which of the following is not true?

a) The least significant bit correspond to a change of V_{max}/2^{N} -1 in the analog signal

b) The resolution of the ADC is V_{max}/2^{N} -1

c) The maximum error in the conversion (or quantization error) is V_{max}/2(2^{N} -1)

d) None of the mentioned

View Answer

Explanation: None of the statements are true.

4. In compact disc (CD) audio technology, the signal is sampled at 44kHz. Each sample is represented by 16bits. What is the speed of the system in bits/second?

a) 1.34 bits/second

b) 2,750 bits/second

c) 704,000 bits/second

d) 1,441,792,000 bits/second

View Answer

Explanation: 44000 X 16 = 704000 bits/s

5. An electrical signal can be represented in either Thevenin form or Norton From. However, Thevenin representation is preferred when

a) The load resistance is very large as compared to the source resistance

b) The load resistance is very low compared to the source resistance

c) There is no preferred case.

d) Both of the cases mentioned are the preferred case

View Answer

Explanation: a is preferred in Thevenin’s case and b in Norton’s case

6. An electrical signal can be represented in either Thevenin form or Norton From. However, Norton representation is preferred when

a) The load resistance is very large as compared to the source resistance

b) The load resistance is very low as compared to the source resistance

c) There is no preferred case

d) Both of the cases mentioned are the preferred case

View Answer

Explanation: a is preferred in Thevenin’s case and b in Norton’s case

7. Consider the DAC (digital to Analog Converter) shown below. Where b_{1}, b_{2}….b_{n} can be either 0 or 1. What will be the value of the output current io, if the digital signal is in the form of b1b2b3…bn.

a) Vref/2R (b1/2+ b2/4 + b3/8….+bn/(2^{N}))

b) 2Vref/R (b1/2+ b2/4 + b3/8….+bn/(2^{N}))

c) Vref/R (b1/2+ b2/4 + b3/8….+bn/(2^{N}))

d) none of the above

View Answer

Explanation: It is the total current that will flow individual resistances.

8. Consider the DAC (digital to Analog Converter) shown below. Where b_{1}, b_{2}….b_{n} can be either 0 or 1. Which is the Most Significant Bit and Least Significant Bit in this case?

a) MSB: b_{N}, LSB: b_{N}

b) MSB: b_{N}, LSB: b_{1}

c) MSB: b_{1}, LSB: b_{N}

d) MSB: b_{1}, LSB: b_{1}

View Answer

Explanation: LSB will have maximum resistance (hence least contribution to the total current) and MSB will have least resistance (Hence maximum contribution to the total current).

9. Consider the DAC (digital to Analog Converter) shown below. Where b_{1}, b_{2}….b_{n} can be either 0 or 1. For v_{ref} = 10V, n = 6, and R= 5000 ohm, which of the following is true?

a) The maximum value of the output current is 1.9375 mA

b) The change in the output current if the LSB is changed from 0 to 1 is 0.03125 mA

c) The change in the output current is the MSB is change from 0 to 1 is 0.5 mA

d) None of the mentioned

View Answer

Explanation: According to the figure, the LSB is given by 10 / 5000

^{6}mA.

10. What is the binary representation of 57?

a) 0011 1101

b) 0101 1001

c) 0111 1001

d) 0011 1001

View Answer

Explanation: The binary equivalent of 57 is 00111001.

**Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.**

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