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

Question 1

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

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

Answer 1

0.67 pf

Question 2

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.

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

Answer 2

15

Question 3

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.

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

Answer 3

55.9 hz

Question 4

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

A)180°
B)225°
C)270°
D)100°

Question 5

We cannot use h-parameter model in high frequency analysis because                          

A)they all can be ignored for high frequencies
B)junction capacitances are not included in it
C)junction capacitances have to be included in it
D)ac analysis is difficult for high frequency using it

Question 6

Which of the statement is incorrect?

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

Question 7

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

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

Question 8

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?

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

Question 9

The technique used to quickly switch off a transistor is by                   

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 10

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

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 11

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

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 12

Switching speed of P+ junction depends on                    

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 13

Fixed voltage regulators and adjustable regulators are often called as

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

Question 14

Linear series regulators are suited for application with

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

Question 15

A series switching regulators

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

Question 16

The switching regulators can operate in

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

Question 17

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

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

Question 18

What should be the frequency range of pulse generator?

A)250 khz
B)40 khz
C)120 khz
D)20 khz

Question 19

Filter used in switching regulator's are also as called

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

Question 20

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

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

Question 21

Which is the most commonly used low voltage switching regulators?

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

Question 22

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                    

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