Electronics Engineering - Online Test
Q1. Which one of the following statements about differential pulse code modulation (DPCM) is true?
Answer : Option D
Explaination / Solution:
DPCM Block diagram
eq[n] is quantized e[n]
e[n] is difference of message signal sample with its prediction.
Q2. Three functions f(t), f2(t) and f3(t) which are zero outside the interval [0, T] are
shown in the figure. Which of the following statements is correct?
Answer : Option C
Explaination / Solution:
For two orthogonal signal f (x) and g(x)
i.e. common area between f x and g x is zero.
Q3. The 3-dB bandwidth of the low-pass signal e-t u(t), where u(t) is the unit step
function, is given by
Answer : Option A
Explaination / Solution:
Q4.
For small increase in VG beyond 1V, which of the following gives the correct description of the region of operation of each MOSFET
Answer : Option D
Explaination / Solution:
For small increase in VG beyond 1 V the n - channel MOSFET goes into saturation as VGS + ive and p - MOSFET is always in active region or triode region.
Q5. For the circuit shown in the following, I0 - I3 are inputs to the 4:1 multiplexers,
R(MSB) and S are control bits. 
The output Z can be represented by
Answer : Option A
Explaination / Solution:
Q6. The L-C circuit shown in the figure has an inductance L = 1mH and a capacitance C = 10µF. 
The L – C circuit of Q.9 is used to commutate a thyristor. Which is initially carrying a current of 5 A as shown in the figure below. The values and initial conditions of L and C are the same as in Q.9. The switch is closed at t=0. If the forward drop is negligible, the time taken for the device to turn off is
Answer : Option A
Explaination / Solution:
No Explaination.
Q7. The open loop transfer function of a unity feedback system is given by 
The gain margin of this system is
The gain margin of this system is
Answer : Option D
Explaination / Solution:
Q8. Consider a wireless communication link between a transmitter and a receiver located in free space, with finite and strictly positive capacity. If the effective areas of the transmitter and the receiver antennas, and the distance between them are all doubled, and everything else remains unchanged, the maximum capacity of the wireless link
Answer : Option C
Explaination / Solution:
Channelcpacity remain same.
Q9. A Hilbert transformer is a
Answer : Option A
Explaination / Solution:
No Explaination.
Q10.
Estimate the output voltage V0 for VG = 1.5 V. [Hints : Use the appropriate current-voltage equation for each MOSFET, based on the answer to Q.57]
Answer : Option C
Explaination / Solution:
Consider for CMOS circuit shown, where the gate voltage v0 of the n-MOSFET is increased from zero, while the gate voltage of the p -MOSFET is kept constant at 3 V. Assume, that, for both transistors, the magnitude of the threshold voltage is 1 V and the product of the trans-conductance parameter is 1mA. V-2
