Question 1

The diode in a half wave rectifier has a forward resistance RF. The voltage is Vmsin?t and the load resistance is RL. The DC current is given by

Accepted Answer

A)  vm/?2rl
B)  vm/(rf+rl) ?
C)  2vm/??
D)  vm/rl B

Question 2

Given that capacitance w.r.t the input node is 2pF and output node is 4pF, find capacitance between input and output node.

Accepted Answer

A)  0.67 pf
B)  1.34pf
C)  0.44pf
D)  2.2pf A

Question 3

Which of the statement is incorrect?

Accepted Answer

A)  at unity gain frequency the ce short circuit current gain becomes 1
B)  unity gain frequency is the same as gain bandwidth product of bjt
C)  gain of bjt decreases at higher frequencies due to junction capacitances
D)  ?- cut-off frequency is one where the ce short circuit current gain becomes ?/2 A

Question 4

A series switching regulators

Accepted Answer

A)  improves the efficiency of regulators
B)  improves the flexibility of switching
C)  enhance the response of regulators
D)  all of the mentioned

Question 5

Filter used in switching regulator's are also as called

Accepted Answer

A)  dc - ac transformers
B)  ac - dc transformers
C)  dc transformer
D)  ac transformer

Question 6

What is the phase shift in RC coupled CE amplifier at lower 3dB frequency?

Accepted Answer

A)  180°
B)  225°
C)  270°
D)  100°

Question 7

Which is the most commonly used low voltage switching regulators?

Accepted Answer

A)  powdered permalloy toroids
B)  fermite ei, u and toroid cores
C)  silicon steel ei butt stacks
D)  none of the mentioned

Question 8

The switching regulators can operate in

Accepted Answer

A)  step up
B)  step down
C)  polarity inverting
D)  all the mentioned

Question 9

Switching speed of P+ junction depends on

Accepted Answer

A)  mobility of minority carriers in p junction
B)  life time of minority carriers in p junction
C)  mobility of majority carriers in n junction
D)  life time of minority carriers in n junction

Question 10

The technique used to quickly switch off a transistor is by

Accepted Answer

A)  reverse biasing its emitter to collector junction
B)  reverse biasing its base to collector junction
C)  reverse biasing its base to emitter junction
D)  reverse biasing any junction

Question 11

The collector current will not reach the steady state value instantaneously because of

Accepted Answer

A)  stray capacitances
B)  resistances
C)  input blocking capacitances
D)  coupling capacitance

Question 12

Which of the following helps in reducing the switching time of a transistor?

Accepted Answer

A)  a resistor connected from base to ground
B)  a resistor connected from emitter to ground
C)  a capacitor connected from base to ground
D)  a capacitor connected from emitter to ground

Question 13

Which of the following is considered to be the most important components of the switching regulator?

Accepted Answer

A)  rc or rlc filter
B)  rl or rlc filter
C)  orc or rl filter
D)  rc, rlc or rl filter

Question 14

For the BJT, ?=?, VBEon=0.7V VCEsat=0.7V. The switch is initially closed. At t=0, it is opened. At which time the BJT leaves the active region?

Accepted Answer

A)  20ms
B)  50ms
C)  60ms
D)  70ms

Question 15

Consider an RC coupled amplifier at low frequency. Internal voltage gain is -120. Find the voltage gain magnitude, when given that collector resistance = 1k?, load = 9k?, collector capacitance is 0. is 0.1?F, and input frequency is 20Hz.

Accepted Answer

A)  120
B)  12
C)  15
D)  -12

Question 16

Fixed voltage regulators and adjustable regulators are often called as

Accepted Answer

A)  series dissipative regulators
B)  shunt dissipative regulators
C)  stray dissipative regulators
D)  all the mentioned

Question 17

Linear series regulators are suited for application with

Accepted Answer

A)  high current
B)  medium current
C)  low current
D)  none of the mentioned

Question 18

The time taken for a transistor to turn from saturation to cut off is

Accepted Answer

A)  inversely proportional to charge carriers
B)  directly proportional to charge carriers
C)  charging time of the capacitor
D)  discharging time of the capacitor

Question 19

Find the 3-dB frequency given that the gain of RC coupled amplifier is 150, the low frequency voltage gain is 100 and the input frequency is 50Hz.

Accepted Answer

A)  50.8 hz
B)  55.9 hz
C)  60hz
D)  100hz

Question 20

Which among the following act as a switch in switching regulator?

Accepted Answer

A)  rectifiers
B)  diode
C)  transistors
D)  relays

Exam 7: Electrical Engineering on Capacitance, Amplifiers, and Switching Regulators