Online Electronics and Communication Engineering Test - Previous Exam Papers Test 7



Loading...  Loading Test...

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.

The amplifier circuit shown below uses a silicon transistor. The capacitors Cc and CE can be assumed to be short at signal frequency and the effect of output resistance r0 can be ignored. If CE is disconnected from the circuit, which one of the following statements is TRUE?

A.
The input resistance Ri increases and the magnitude of voltage gain Av decreases
B.
The input resistance Ri decreases and the magnitude of voltage gain Av decreases
C.
Both input resistance Ri and the magnitude of voltage gain Av decrease
D.
Both input resistance Ri and the magnitude of voltage gain Av increase

Your Answer: Option (Not Answered)

Correct Answer: Option A

Explanation:

Given circuit after removing CE will behave as current-series feedback.

Overall voltage gain will decrease as feedback signal comes into picture and since it is current-series feedback, input impedance increases.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


2.

With a line charge along z-axis the field intensity is E = ; which of the following figure shows an exact field distribution?

A.
B.
C.
D.

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

The given figure fails to show the symmetry with respect to Φ.

The figure shows symmetry with respect to f, also the length of arrow is decreasing away from the charge shows that magnitude E is decreasing away from line charge.

But problem with this figure is longest lines must be shown in most crowded region.

Here we use lines of fixed segments but different thickness. But this attempt also makes the region crowded near origin.

This figure shows compromise. A symmetrical distribution of lines (at every 45°) shows azimuthal symmetry and arrowheads show direction.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


3.

The impulse response h(t) of a linear time-invariant continuous time system is described by h(t) = exp (at) u(t) + exp (βt) u (- t), where u(t) denotes the unit step function, and a and β are constants. This system is stable if

A.
a is positive and β is positive
B.
a is negative and β is negative
C.
a is positive and β is negative
D.
a is negative and β is positive

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

h(t) = e+atu(t) + eβtu(- t)

For h(t) to be stableh(t) dt < ∞

It will happen when a is negative and β is positive.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


4.

The dual transform of the given network as

A.
B.
C.
D.
none of the above

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Dual of R → G

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


5.

The following statements are true with respect to "Cascode Amplifier".

  1. The reduction in h12 and Miller capacitance result in negligible reverse internal feedback.
  2. A's is large loads cannot be connected.
  3. As a narrow band amplifier, it provides small range of cμ is reduced.
  4. As a narrow band amplifier it provides small range of frequencies parameters the effect of cμ reduces.

A.
only 1
B.
only 1 and 4
C.
only 2 and 4
D.
only 1 and 3

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

Cascode is a wide band amplifier and it provides wide range of frequencies than CE stage and as is large, large loads can be connected.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


6.

For a given transfer function: Damping ratio is:

A.
0.707
B.
0.695
C.
1.414
D.
0.798

Your Answer: Option (Not Answered)

Correct Answer: Option A

Explanation:

1 + G(s)H(s) = s2 + 2s + 2

ωn = 2 , 2εeωn = 2, εe = = 0.707.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


7.

If the open-loop transfer function is a ratio of a numerator polynomial of degree 'm' and a denominator polynomial of degree 'n', then the integer (n - m) represents the number of:

A.
breakaway points
B.
unstable poles
C.
separate root loci
D.
asymptotes

Your Answer: Option (Not Answered)

Correct Answer: Option D

Explanation:

Asymptotes.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


8.

The expression given is F(A, B , C, D, E, F, G, H) = (33, 48, 102, 158, 222, 229, 233, 243, 255); then the __________ and __________ minterms are grouped together into dual and variable __________ is reduced using the dual

A.
243, 233, D
B.
222, 158, B
C.
243, 255, A
D.
229, 243, E

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

We use Quine - McCluskey method of reduction :

We can observe that minterms 158 and 222 can be grouped together to reduce the variable 'B'.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


9.

A uniform plane wave in the free space is normally incident on an infinitely thick dielectric slab (dielectric constant εr = 9). The magnitude of the reflection coefficient is

A.
0
B.
0.3
C.
0.5
D.
0.8

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

Thus reflection coefficient = = - 0.5

Thus magnitude is 0.5 .

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


10.

The continuous time system with impulse response h(t) u(t) is stable, if __________ (n is even).

A.
a = 0
B.
a > 0
C.
a < 0
D.
none of these

Your Answer: Option (Not Answered)

Correct Answer: Option C

Explanation:

h(t) =

consider

ax = x

ax = x2

a = x

For h(t) to be bounded, exponential term should have a negative power.

i.e. e-t will have response as shown.

Hence should be < 0

a < 0.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


11.

A white noise X(t) with two-sided power spectral density 1 x 10-10 W/Hz is input to a filter whose magnitude squared response is shown below.

The power of the output process Y(t) is given by

A.
5 x 10-7W
B.
1 x 10-6W
C.
2 x 10-6W
D.
5 x 10-6W

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

Since bandwidth is 10 kHz, thus output power is 10 x 10-11 x 10 x 103 = 1 x l0-6 W.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


12.

A germanium diode has a reverse saturation current of 30 μA at 125°C and forward current of 1 mA at a forward potential of 0.8 V and the reverse potential is 0.6 V What are its dynamic forward and reverse resistance at this temperature.

A.
10.7 Ω, 70 kΩ
B.
34 Ω, 20 kΩ
C.
80 Ω, 20 kΩ
D.
800 Ω, 40 kΩ

Your Answer: Option (Not Answered)

Correct Answer: Option B

Explanation:

We have,

I = I0•(eV/nVT -1)

For forward voltage greater than few teeth's of volts, I >> I0

Forward dynamic resistance,

= 34.3 Ω

Reverse dynamic resistance = = 20 kΩ.

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


13.

In the circuit below, the diode is ideal. The voltage V is given by

A.
min(Vi, 1)
B.
max(Vi, 1)
C.
min (-Vi, 1)
D.
max (-Vi, 1)

Your Answer: Option (Not Answered)

Correct Answer: Option D

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


14.

The correct sequence of subsystems in an FM receiver is

A.
Mixer, RF amplifier, Limiter, IF amplifier. Discriminator, Audio amplifier
B.
RF amplifier, Mixer, IF amplifier, Limiter, Discriminator, Audio amplifier
C.
RF amplifier, Mixer, Limiter, Discriminator IF amplifier, Audio amplifier
D.
Mixer, IF amplifier, RF amplifier, Audio amplifier, Discriminator

Your Answer: Option (Not Answered)

Correct Answer: Option B

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


15.

A fully charged mobile phone with a 12 V battery is good for a 20 minute talktime. Assume that, during the talk time, the battery delivers a constant current of 2 A and its voltage drops linearly from 12 V to 10 V as shown in the figure. How much energy does the battery deliver during this talk time?

A.
220 J
B.
12 kJ
C.
13.2 kJ
D.
14.4 kJ

Your Answer: Option (Not Answered)

Correct Answer: Option C

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


16.

An audio signal is to be transmitted digitally. Which is the system best suited for good fidelity?

A.
8 bit PCM
B.
13 bit PCM
C.
32 bit PCM
D.
PCM system with non-uniform quantizer

Your Answer: Option (Not Answered)

Correct Answer: Option D

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


17.

When transistor is used as a switch __________ is defined as the interval which elapses between the transition of input waveform and the time when to transition to 90% of Ic(sat).

A.
storage time
B.
fall time
C.
turn-on time
D.
turn-off time

Your Answer: Option (Not Answered)

Correct Answer: Option A

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


18.

For the circuit of the following figure, with an ideal op-amp, the maximum phase shift of the output with reference to the input is :

A.
B.
90°
C.
-90°
D.
± 180°

Your Answer: Option (Not Answered)

Correct Answer: Option D

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


19.

The junction capacitance of a linearly graded pn junction (with applied voltage = VB) is proportional to

A.
B.
C.
D.

Your Answer: Option (Not Answered)

Correct Answer: Option D

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


20.

Assertion (A): An unbiased p-n junction develops a built-in potential at the junction with the n-side positive and the p-side negative.

Reason (R): The p-n junction behaves as a battery and supplies current to a resistance connected across its terminals.

A.
Both A and R are individually true and R is the correct explanation of A
B.
Both A and R are individually true but R is not the correct explanation of A
C.
A is true but R is false
D.
A is false but R is true

Your Answer: Option (Not Answered)

Correct Answer: Option C

Learn more problems on : Exam Questions Papers

Discuss about this problem : Discuss in Forum


Submit your test now to view the Results and Statistics with answer explanation.