Electronics Engineering - Online Test
Q1. In the circuit shown below, for the MOS transistors, 
and
the threshold voltage VT = 1 V. The voltage Vx at the source of the upper
transistor is
and
the threshold voltage VT = 1 V. The voltage Vx at the source of the upper
transistor is
Answer : Option C
Explaination / Solution:
Given circuit is shown below.
Thus our assumption is true and Vx = 3 V.
For transistor M2,
Since 
thus M2 is in saturation.
By assuming M1 to be in saturation we have
thus M2 is in saturation.
By assuming M1 to be in saturation we haveTaking positive root,
Thus our assumption is true and Vx = 3 V.
Q2. The Boolean function realized by the logic circuit shown is
Answer : Option D
Explaination / Solution:
Output of the MUX can be written as
Q3. In the following circuit, the switch S is closed at t = 0. The rate of change of
current 
is given by
is given by
Answer : Option B
Explaination / Solution:
Initially i(0-) = 0 therefore due to inductor i(0+) = 0. Thus all current Is will
flow Is in resistor R and voltage across resistor will be IsRs. The voltage across
inductor will be equal to voltage across Rs as no current flow through R.
Q4. The signal x(t) is described by
Two of the angular frequencies at which its Fourier transform becomes zero are
Answer : Option A
Explaination / Solution:
Q5.
The magnitude of frequency responses of an underdamped second order system is 5 at 0 rad/sec and peaks to 10/√3 at 5√2 rad/sec. The transfer function of the system is
Answer : Option C
Explaination / Solution:
Q6.
A communication channel with AWGN operating at a signal to noise ration SNR >> 1 and bandwidth B has capacity C1. If the SNR is doubled keeping constant, the resulting capacity C2 is given by
Answer : Option B
Explaination / Solution:
Q7. For a BJT the common base current gain α = 0.98 and the collector base
junction reverse bias saturation current ICO = 0.6 μA. This BJT is connected in
the common emitter mode and operated in the active region with a base drive
current IB = 204 A. The collector current IC for this mode of operation is
Answer : Option D
Explaination / Solution:
In active region, for common emitter amplifier,
Substituting ICO = 0.6 μA and IB = 204 μA in above eq we have,
IC = 1.01 mA
Q8. In a microprocessor, the service routine for a certain interrupt starts from a fixed location of memory which cannot be externally set, but the interrupt can be delayed or rejected Such an interrupt is
Answer : Option D
Explaination / Solution:
Vectored interrupts : Vectored interrupts are those interrupts in which program control transferred to a fixed memory location.
Maskable interrupts : Maskable interrupts are those interrupts which can be rejected or delayed by microprocessor if it is performing some critical task.
Q9. The Thevenin equivalent impedance Zth between the nodes P and Q in the
following circuit is
Answer : Option A
Explaination / Solution:
Killing all current source and voltage sources we have,
Q10. A discrete time linear shift - invariant system has an impulse response h[n] with h[0] = 1,h[1] =- 1,h[2] = 2, and zero otherwise The system is given an input sequence x[n] with x[0] = x[2] = 1, and zero otherwise. The number of nonzero samples in the output sequence y[n], and the value of y[2] are respectively
Answer : Option D
Explaination / Solution:
