Electronic Science - Online Test
Q1. Consider the following statements for a metal oxide semiconductor field effect transistor
(MOSFET):
P: As channel length reduces, OFF-state current increases.
Q:As channel length reduces, output resistance increases.
R: As channel length reduces, threshold voltage remains constant.
S: As channel length reduces, ON current increases.
Which of the above statements are INCORRECT?
Answer : Option C
Explaination / Solution:
Q2. 
In the circuit shown below, the op-amp is ideal, the transistor has VBE = 0.6 V and β= 150. Decide whether the feedback in the circuit is positive or negative and determine the voltage V at the output of the op-amp.
Answer : Option D
Explaination / Solution:
The circuit is shown in fig below
Q3. If the diameter of earth is , then its capacitance will be
Answer : Option D
Explaination / Solution:
the capacitance of a spherical conductor of radius R is
Q4. For parallel RLC circuit, which one of the following statements is NOT correct ?
Answer : Option D
Explaination / Solution:
A parallel RLC circuit is shown below :
Input impedance
Q5. What is the voltage Vout in the following circuit?
Answer : Option C
Explaination / Solution:
The transfer characteristics of the CMOS inverter is as follows
Since the inverter is connected in feedback loop formed by connecting
10XΩ resistor between
the output and input, the output goes and stays at the middle of the characteristics
Va Switching threshold of inverter
Q6. A 3-input majority gate is defined by the logic function M(a,b,c) = ab + bc + ca. Which one of the following gates is represented by the function 
Answer : Option B
Explaination / Solution:
3 input majority gate is given as
M(a,b,c) = ab + bc + ca
We have to obtain 
We obtain truth table for the function as
So, the function is odd number of 1’s detector. This function represent the 3-input XOR gate.
Q7. 
In the circuit shown, the switch S is open for a long time and is closed at t = 0. The current i (t) for t ≥ 0+is
Answer : Option A
Explaination / Solution:
When the switch S is open for a long time before t < 0, the circuit is
At t = 0, inductor current does not change simultaneously, So the circuit is
Current is resistor (AB)
i(0) = 0.75/2 = 0.375 A
Similarly for steady state the circuit is as shown below
B = 0.375 - 0.5 =- 0.125
Q8. Consider a silicon sample at T=300K, with a uniform donor density 
illuminated uniformly such that the optical generation rate
is 
throughout the sample. The incident radiation is turned off at 𝑡=0.
Assume low-level injection to be valid and ignore surface effects. The carrier lifetimes are 
illuminated uniformly such that the optical generation rate
is throughout the sample. The incident radiation is turned off at 𝑡=0.
Assume low-level injection to be valid and ignore surface effects. The carrier lifetimes are The hole concentration at t = 0 and the hole concentration at t = 0.3μs, respectively, are
Answer : Option A
Explaination / Solution:
Q9. The Boolean expression 
converted into the canonical product of sum (POS) form is
converted into the canonical product of sum (POS) form is
Answer : Option A
Explaination / Solution:
We have the SOP Boolean form,
Hence, in POS form, we have
Q10. The current I in the circuit shown is
Answer : Option A
Explaination / Solution:
