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Design of Electronic Devices & Circuits - short answer questions from AMIE exams (Winter 2019)

Choose the correct answer for the following (10 x 2)

1. An example of a military-grade op-amp with a higher slew rate is
(a) 741
(b) 741 C
(c) 741 A
(d) 741 S

2. A non-inverting amplifier with a gain of 100 is nulled at 25°C. Determine the output voltage if the temperature rises to 40°C for an offset voltage drift of 0.15 MV/°C.
(a) 600 MV
(b) 450 MV
(c) 225 MV
(d) 60 MV

3. An example of a negative regulator is
(a) LM117
(b) LM137
(c) LM217
(d) LM317

4. The operational transconductance amplifier outputs a current proportional to its
(a) Input voltage
(b) Input resistance
(c) Input capacitance
(d) Input conductance

5. A second-order low-pass filter has a roll-off rate of
(a) - 40 dB/octave
(b) - 40 dB/decade
(c) - 20 dB/octave
(d) - 20 dB/decade

6. A quadrature oscillator generates both 
(a) Cosine wave and rectangular wave 
(b) Cosine wave and triangular wave 
(c) Cosine wave and sawtooth wave 
(d) Cosine wave and sine wave

7. A pulse position modulator can be built using a 555
(a) Monostable multivibrator
(b) One shot multivibrator
(c) Astable multivibrator
(d) Schmitt trigger

8. A PLL that is very useful as an FSK. demodulator is
(a) 565 PLL
(b) 564 PLL
(c) 562 PLL
(d) 561 PLL

9. A 64-input multiplexer can be built using
(a) Thirty-two two input MUXs
(b) Nine eight input MUXs
(c) Eight eight input MUXs
(d) Sixteen four input MUXs

10. Consider a 1024-bit ROM. How many address bits does it require?
(a) 16
(b) 12
(c) 10
(d) 8

Answers

1. (d) Op-amp ICs varying in the version of 741 are highly approved or sanctioned for military-grade since the temperature range lies within -55° to 125°C. So, as the temperature level range display variations, the op-amp IC741 are further sub-categorized under 741C, 741A & 741E & so on. Besides these, 741S & 741SC are recommended for military and commercial aspects due to the high slew rate.

2. (c) Input offset voltage due to temperature rise = 0.15 mV/°C x (40°C -25°C) = 2.25 mV. Since this is an input change, the output voltage will change by
Vo = Vos x ACL = 2.25 mV x 100 = 225 mV
This could represent a very major shift in the output voltage.

3. (b) 

4. (d) The operational transconductance amplifier produces an output voltage proportional to an input current. 

5. (b) Second Order (or two-pole) Filters consist of two RC filter sections connected together to provide a -40dB/decade roll-off rate.


6. (d) 


7. (a)

8. (a) 

9. (b) To build 64-input MUX: 
1st stage = 64/8=8
2nd  stage = 8/8=1
The sum will give the total number of 8-input MUXs. needed 
n = 8 + 1 = 9

10. (c) The size of the ROM is 1024 × 8 = 210× 8 Here 10 indicates the address bus. Therefore, the address bus with a ROM of size 1024 × 8 bits is 10 bits.

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The study material for AMIE/Junior Engineer exams is available at https://amiestudycircle.com
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