Free Printable ECA ASSIGNMENT 1

1.

THE GAIN OF AN AMPLIFIER IS EXPRESSED IN db BECAUSE-----------

a)

IT IS A SIMPLE UNIT

b)

Calculations become easy

c)

Human ear response is logarithmic

d)

None of the above

2.

WHAT IS THE MAIN FUNCTION OF AN AMPLIFIER IN AN ELECTRONIC CIRCUIT?

a)

To increase voltage

b)

To filter signals

c)

To convert AC to DC

d)

To decrease noise

3.

WHICH COMPONENT IS ESSENTIAL FOR AN AMPLIFIER TO FUNCTION PROPERLY?

a)

Inductor

b)

Transistor

c)

Capacitor

d)

Resistor

4.

To draw dc equivalent circuit for a CE amplifier we should___.

a)

Reduce all ac sources to zero

b)

open all capacitors

c)

Reduce all ac sources to zero & open all capacitors

d)

Reduce all ac sources to zero & short all capacitors

5.

The most desirable feature of transformer coupling is its_______.

a)

ability to eliminate hum from the output

b)

ability to provide impedance matching between stages

c)

higher voltage gain

d)

wider frequency range

6.

A cascaded amplifier stage is equivalent to____.

a)

common emitter stage followed by common base stage.

b)

common base stage followed by an emitter follower.

c)

an emitter follower stage followed by common base stage.

d)

common base stage followed by a common emitter stage

7.

Which type of coupling produces minimum interference with frequency response?

a)

RC coupling

b)

transformer coupling

c)

direct coupling

d)

impedance coupling

8.

For an amplifier, the coupling method which gives highest gain in______.

a)

impedance coupling

b)

transformer coupling

c)

capacitance coupling

d)

resistance coupling

9.

The source of harmonic distortion in RC coupled transistor amplifier is usually__________.

a)

power supply

b)

capacitor

c)

R-C circuit

d)

transistor

10.

In a CE transistor amplifier, when collector emitter voltage increases______.

a)

the instantaneous operating point moves up the load line

b)

the instantaneous operating point moves down the load line

c)

none of themload current increases

11.

In case of transistor amplifier the emitter resistance R_E is removed, then______.

a)

the gain of the amplifier will reduce

b)

heat sink will not be required.

c)

Q-point will be unstable

d)

base to emitter junction will be less forward biased.

12.

The gain of a transistor amplifier falls at high frequencies due to the_________.

a)

internal capacitance of the device

b)

coupling capacitor at the input

c)

skin effect

d)

coupling capacitor at the output

13.

What is the effect of cascading the amplifier stages?

a)

To increase voltage gain & increase the bandwidth

b)

To increase voltage gain & reduce the bandwidth

c)

To decrease voltage gain & increase the bandwidth

d)

To decrease voltage gain & reduce the bandwidth

14.

Power gain in decibels is equal to voltage gain in decibels only when________.

a)

input impedance is zero

b)

output impedance is zero

c)

never

d)

input impedance is equal to output impedance

15.

The amplifier gain varies with frequency. This happens mainly due to________.

a)

miller effect

b)

logarithmic increase in its output power

c)

interstage transformers

d)

presence of external & internal capacitance.

16.

The bandwidth of an amplifier may be increased by____________.

a)

reducing the stray capacitance to the minimum possible

b)

cascading to amplifier stages

c)

reducing the capacitance of bypass capacitors

d)

increasing input signal frequency

17.

In an amplifier, the coupling capacitors are are used for___________.

a)

limiting the bandwidth

b)

matching the impedances

c)

controlling the output

d)

preventing of dc mixing with input or output

18.

In an RC coupled common emitter amplifier______________.

a)

Cc affects the high frequency response & C_E affects low frequency response

b)

both Cc & C_E affects high frequency response

c)

both Cc & C_E affects low frequency response

d)

Cc affects the low frequency response & C_E affects high frequency response

19.

In RC coupled amplifier, the gain decreases in the frequency response due to the_________.

a)

coupling capacitor at low frequency & bypass capacitor at high frequency

b)

coupling capacitor at high frequency & bypass capacitor at low frequency

c)

coupling junction capacitance at low frequency & coupling capacitor at high

frequency

d)

device junction capacitor at high freq. & coupling capacitor at low frequency

20.

The purpose of impedance matching between the output of previous stage & input of next stage in a cascaded amplifier is_________.

a)

to achieve high efficiency

b)

to achieve maximum power transfer

c)

to achieve reduced distortion

d)

to achieve reduced noise.

21.

The decibel gain of cascaded amplifier is equal to_____________.

a)

product of individual stage gain

b)

sum of individual stage gain

c)

ratio of stage gains

d)

product o voltage & current gains

22.

The main component responsible for lowering of gain in an RC coupled amplifier in low frequency range is__________.

a)

biasing system

b)

Resistor R_E

c)

coupling capacitor Cc

d)

transistor itself

23.

In an RC coupled amplifier, the voltage gain is___________.

a)

remains almost constant over a range of frequency

b)

always increases with frequency

c)

always decreases with frequency

d)

increases with supply voltage

24.

The most desirable feature of transformer coupling is its_______.

a)

ability to eliminate hum from the output

b)

ability to provide impedance matching between stages

c)

higher voltage gain

d)

wider frequency range

25.

To draw dc equivalent circuit for a CE amplifier we should___.

a)

Reduce all ac sources to zero

b)

open all capacitors

c)

Reduce all ac sources to zero & open all capacitors

d)

Reduce all ac sources to zero & short all capacitors

26.

What is the primary purpose of using bypass capacitors in an amplifier circuit?

a)

To increase the input impedance

b)

To stabilize the gain

c)

To reduce power consumption

d)

To prevent AC signals from affecting DC biasing

27.

In a common emitter amplifier, the phase shift between input and output is______.

a)

0 degrees

b)

90 degrees

c)

180 degrees

d)

270 degrees

28.

Which of the following factors primarily affects the frequency response of an amplifier?

a)

Capacitance and inductance in the circuit

b)

Power supply voltage

c)

Load resistance

d)

Transistor type

29.

In a FET Amplifier the source follower is a

a)

CS Amplifier

b)

CG amplifier

c)

CD amplifier

d)

none of above

30.

In a RC coupled amplifier ,the coupling capacitor

a)

limits the low frequency response

b)

limits the high frequency response

c)

independent of collector current

d)

proportional to square of the collector current

31.

The capacitive reactance is equal to

a)

$\frac{1}{2\pi f_c}$

b)

$2\pi f_c$

c)

$\pi f_c$

d)

$\frac{1}{\pi f_c}$

32.

The capacitive effects of transistor junction manifest themselves in

a)

low frequency

b)

middle frequency

c)

high frequency

d)

all the babove

33.

The emitter diffusion capacitance for a transistor is

a)

inversely proportional to the collector current

b)

directly proportional to the collector current

c)

independent of the collector current

d)

optional to the square of the collector current

34.

The voltage gain of an amplifier decreases at 20dB/decade above 100kHz. If the midband frequency gain is 80bB,what is the value of the voltage gain at 2MHz?

a)

60dB

b)

52dB

c)

54dB

d)

64dB

35.

$g_m$ The FT of a BJT is related to its $g_m$ , $C_{\pi}$ and $C_{\mu}$ as follows

a)

$f_T=\frac{C_{\pi}+C\mu}{g_m}$

b)

$f_T=\frac{2\pi\left(C_{\pi}+C_{\mu}\right)}{g_m}$

c)

$f_T=\frac{g_m}{C_{\pi}+C_{\mu}}$

d)

$f_T=\frac{g_m}{2\pi\left(C_{\mu}+C_{\pi}\right)}$

36.

Half power gain is the maximum gain minus

a)

6dB

b)

12dB

c)

3dB

d)

2dB

37.

$\beta$

The cut-off frequency $\beta$ is found from

a)

CC configuration

b)

CE configuration

c)

CB configuration

d)

none of the above.

38.

$\alpha$ The value of $\alpha$ cut-off frequency is

a)

greater than the $\beta$ cut-off frequency

b)

smaller than the $\beta$ cut-off frequency

c)

equal to the $\beta$ cut -off frequency

d)

none of the above

39.

The reference for dBm is

a)

1 milliwatt

b)

1 watt

c)

10 watts

d)

1 mega watts

40.

$\alpha$

The $\alpha$ cut-off frequency is found from

a)

CC configuration

b)

CE configuration

c)

CB configuration

d)

none of the above

41.

In a FET amplifier , the capacitor $C_{gs}$ and $C_{gd}$ typically vary from

a)

1 to 10pF

b)

1 to 10 $\mu$ F

c)

1 to 10 F

d)

none of the above

42.

The input impedance of a CS amplifier circuit is very high

a)

high frequency

b)

low frequency

c)

mid frequency

d)

zero frequency

43.

The output impedance will be lower at higher frequencies, thereby reducing the gain because

a)

the capacitive reactance's decreases with increase in frequency

b)

Capacitive reactance increases with the increase in frequency

c)

Capacitive reactance decreases with the decrease in frequency

d)

none of the above

44.

Another name for positive feedback

a)

degenerative feedback

b)

regenerative feedback

c)

inverse feedback

45.

The regenerative feedback amplifier overall gain is given by

a)

A_f = A/(1+Aβ)

b)

A_f = 1-Aβ

c)

A_f = A/(1-Aβ)

d)

A_f = 1+Aβ

46.

The degenerative feedback amplifier overall gain is given by

a)

A_f = A/(1+Aβ)

b)

A_f = 1+Aβ

c)

A_f = A/(1-Aβ)

d)

A_f = 1-Aβ

47.

Negative Feedback is frequently used in ...............................circuits

a)

Amplifier

b)

Permanent

c)

microprocessor

d)

All the Above

48.

Positive feedback increases amplifier gain

a)

true

b)

false

c)

insufficient data

49.

positive feedback is used in

a)

tuned circuit

b)

rectifiers

c)

amplifiers

d)

oscillators

50.

When negative voltage feedback is applied to an amplifier, its voltage gain ............

a)

is increased

b)

is reduced

c)

remains the same

d)

none of the above

51.

Negative feedback is employed in .......

a)

oscillators

b)

rectifiers

c)

amplifiers

d)

none of the above

52.

One condition for oscillation is ...........

a)

a phase shift around the feedback loop of 180º

b)

a gain around the feedback loop of onethird

c)

a phase shift around the feedback loop of 0º

d)

a gain around the feedback loop of less than 1

53.

Hartley oscillator is commonly used in ...........

a)

radio receivers

b)

radio transmitters

c)

TV receivers

d)

none of the above

54.

For class B operation, the collector current flows for

a)

The whole cycle

b)

Half the cycle

c)

Less than half a cycle

d)

Less than a quarter of a cycle

55.

Transformer coupling is an example of

a)

Direct coupling

b)

AC coupling

c)

DC coupling

d)

Impedance coupling

56.

An audio amplifier operates in the frequency range of

a)

0 to 20 Hz

b)

20 Hz to 2 kHz

c)

20 to 20 kHz

d)

Above 20 kHz

57.

A tuned RF amplifier is

a)

Narrowband

b)

Wideband

c)

Direct-coupled

d)

A dc amplifier

58.

The first stage of a preamp is

a)

A tuned RF stage

b)

Large signal

c)

Small signal

d)

A dc amplifier

59.

For maximum peak-to-peak output voltage, the Q point should be

a)

Near saturation

b)

Near cutoff

c)

At the center of the ac load line

d)

At the center of the dc load line

60.

Push-pull is almost always used with

a)

Class A

b)

Class B

c)

Class C

d)

All of the above

61.

One advantage of a class B push-pull amplifier is

a)

No quiescent current drain

b)

Maximum efficiency of 78.5 percent

c)

Greater efficiency than class A

d)

All of the above

62.

Class C amplifiers are almost always

a)

Transformer-coupled between stages

b)

Operated at audio frequencies

c)

Tuned RF amplifiers

d)

Wideband

63.

The collector current of a class C amplifier

a)

Is an amplified version of the input voltage

b)

Has harmonics

c)

Is negatively clamped

d)

Flows for half a cycle

64.

The bandwidth of a class C amplifier decreases when the

a)

Resonant frequency increases

b)

Q increases

c)

Inductive reactance decreases

d)

Load resistance decreases

65.

The power rating of a transistor can be increased by

a)

Raising the temperature

b)

Using a heat sink

c)

Using a derating curve

d)

Operating with no input signal

66.

The AC load line is the same as the DC load line when the AC collector resistance equals the

a)

DC emitter resistance

b)

AC emitter resistance

c)

DC collector resistance

d)

Supply voltage divided by collector current

67.

If Rc = 100 Ω and Re = 180 Ω, the AC load resistance equals

a)

64 Ω

b)

90 Ω

c)

100 Ω

d)

180 Ω

68.

The AC load line usually

a)

Equals the DC load line

b)

Has less slope than the DC load line

c)

Is steeper than the DC load line

d)

Is horizontal

69.

In a class A amplifier, the collector current flows for

a)

Less than half the cycle

b)

Half the cycle

c)

Less than the whole cycle

d)

The entire cycle

70.

With class A, the output signal should be

a)

Unclipped

b)

Clipped on positive voltage peak

c)

Clipped on negative voltage peak

d)

Clipped on negative current peak

71.

The instantaneous operating point swings along the

a)

AC load line

b)

DC load line

c)

Both load lines

d)

Neither load line

72.

The current drain of an amplifier is the

a)

Total AC current from the generator

b)

Total DC current from the supply

c)

Current gain from base to collector

d)

Current gain from collector to base

73.

The power gain of an amplifier

a)

Is the same as the voltage gain

b)

Is smaller than the voltage gain

c)

Equals output power divided by input power

d)

Equals load power

74.

Heat sinks reduce the

a)

Transistor power

b)

Ambient temperature

c)

Junction temperature

d)

Collector current

75.

When the ambient temperature increases, the maximum transistor power rating

a)

Decreases

b)

Increases

c)

Remains the same

d)

None of the above

76.

If the load power is 300 mW and the DC power is 1.5 W, the efficiency is

a)

0

b)

2 percent

c)

3 percent

d)

20 percent

77.

The maximum efficiency of a class B push-pull amplifier is

a)

25 percent

b)

50 percent

c)

78.5 percent

d)

100 percent

78.

A small quiescent current is necessary with a class AB push-pull amplifier to avoid

a)

Crossover distortion

b)

Destroying the compensating diodes

c)

Excessive current drain

d)

Loading the driver stage

ECA ASSIGNMENT 1

Total questions: 78

Worksheet time: 36mins

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