7.LARGE SIGNAL AMPLIFIERS
1. the class A amplifier has [ ]
a)high efficiency, distortion b)low efficiency, high distortion c) )lowefficiency, distortion d)none
2. In a class A amplifier the circuit efficiency can be increased by using [ ]
a)low dc power input b)transformer coupled load c)low rating transistor d)direct coupled load
3. The maximum conversion efficiency of classB amplifier is [ ]
a)78.5%b)63.33%c)100%d)50%
4 . The main function of the transformer used in the output of power amplifier is to [ ]
a)increase the output power b)increase the voltage gain c)match the load resistance with output resistance d)none of these
5. when compared to a class B amplifier ,a class A power amplifier has [ ]
a)more efficiency b)less distortion c)is not susceptible to power supply d)none of these
6. The maximum overall efficiency of a transformer –coupled classA amplifier [ ]
a)25% b)50% c)78.5% d)87.5%
7. The amplifier that suffers from the problem of cross over distortion is [ ]
a)classA b)classB c)classC d)classAB
8. It is theoretically possible to achieve 100% efficiency using a [ ]
a)classD amplifier b)classA amplifier c) classAB amplifier d)classC amplifier
9. classc amplifiers are generally used as [ ]
a)power amplifiers b)RF amplifiers c)audio amplifiers d)none of these
10. The primary function of a phase inverter is to change the phase of a signal by [ ]
a)90▪ b)120▪ c)360▪ d)180▪
11.Thermal resistance has the unit of [ ]
a)Ω b)Ω/W c)0C d) 0C/W
12.Heat sinks are used in power transistors to [ ]
a)reduce the transistor power b)reduce the junction temperature c)increase the ambient temperature d)increase the collector current
13.In push-pull amplifiers biasing is usually not required because [ ]
a)dcc battery vcc is employed b)power transistors do not require biasing c)heat sink is used with the transistor d)transistors are working in class-B operations
14.The main advantage of a class B push-pull amplifier is free from [ ]
a)any circuit imbalances b)unwanted noise c)even order harmonic distortion d)dc magnetic saturation effects
15.The ratio of signal power delivered to load to dc power supplied to an amplifier is [ ]
a)gain factor b)loss factor c)conversion factor d)none
16.The dissipation at the collector is zero in the quiescent state and increases with excitation in the case of a [ ]
a)class-A series fed amplifier b)class-A transformer coupled amplifier c)class AB amplifier d)classB amplifier
17.The output of a class-B amplifier [ ]
a)consists of positive haif cycle only
b)is distortion free
c)is like the output of a full wave rectifier
d)comprises short duration current pulses
18.Th use of class AB operation in large signal amplifiers is to [ ]
a)get maximum efficiency b)remove even harmonics c)overcome crossover distortion d)reduce collector dissipation
19. Even harmonics not present in the out put of [ ]
a) class a b)class A c)class c d)class AB
20.Cross over distortion in class B amplifiers can be eliminated by modifying the configaration [ ]
a) class B push pull amplifier b)class A c)class c d)class AB
21.The collector current in quiesciecnt condition is zero when [ ]
a)amplifier working in class A operation
b) amplifier working in class AB operation
c) amplifier working in class B operation
d)none
22.The transformer coupling in a class A amplifier is [ ]
a)distortion free b)bulky c)costly d)efficient
23.In a class A amplifier the current in the output circuit flows for [ ]
a)less than 90▪ b)90▪ c)180▪ d)360▪
24.The maximum conversion efficiency for a classA amplifier is [ ]
a)78.5% b)63.33% c)100% d)50%
25.The harmonic component that has the main contribution in the total distortion in an amplifier is [ ]
a)second harmonic component b)third harmonic component c)fourth harmonic component d)fifth harmonic component
8.TUNED AMPLIFIERS
1. A parallel LC circuit at resonance frequencyoffers [ ]
a)low impedance b)zero impedance c)high impedance d)infinite impedance
2. At frequencies greater than resonant frequency the parallel tuned circuit is [ ]
a)capacitive b)inductive c)resistive d)none
3. At frequencies lesser than resonant frequency the parallel tuned circuit is [ ]
a)capacitive b)inductive c)resistive d)none
4. The effective quality factor ofa tuned amplifier is called [ ]
a)risk factor b)loss factor c)circuit magnification factor d)dissipatin factor
5. The bandwidth of cascading single tuned amplifier [ ]
a)increases b)decreases c)maintains same d)all the above
6. A radio frequency transmitter uses a ----------tuned amplifier [ ]
a)class A b)classAB c)classC d)noe of these
7. If a tuned circuit has a resonant frequency of 1MHZ & a bandwidth of 20MHZ its Q –factor is [ ]
a)20 b)50 c)100 d)500
8. If the Q –factor of a single tuned amplifier is doubled then its bandwidth will be [ ]
a)same b)half c)double d)four times
9. The function of tuned circuit in tuned amplifier is [ ]
a) allows the dc signal b)reject dc and allow other frequencies c)passing all frequencies
d)selecting particular frequency & rejecting all other frequencies
10. A parallel tuned circuit ia also known as [ ]
a)matched circuit b)notch circuit c)resonant circuit d) anti-resonant circuit
11 . What factors govern the selectivity of a single tuned amplifier ? [ ]
a. resonant frequency and gain b. quality factor and bandwidth
c. quality factor and gain d. gain and bandwidth
12. The harmonic distortion of an ideal tuned amplifier is [ ]
a. unity b. zero c. infinity d. depends on tuned circuit
13. In tuned amplifiers, harmonic distortion is very small because, at these frequencies [ ]
a. the impedance is high and gain is low b. the impedance is low and gain is high
c. the impedance and gain of the amplifier becomes high
d. the impedance and gain of the amplifier becomes negligible
14. The Band width of an ideal tuned amplifier is [ ]
a. unity b. zero c. infinity d. depends on tuned circuit
15. In a single tuned transformer coupled amplifier, the output is taken by [ ]
a. capacitive coupling b. inductive coupling c. resistive coupling d. frequency coupling
16. If two or more tuned circuits are cascaded and tuned to the same frequency, then the overall bandwidth [ ]
a. decreases b. increases c. equal to a single stage d. increases by number of stages cascaded
17. If the number of stages in stagger tuned amplifier is increased, then the resultant voltage gain is [ ]
a. decreases b. increases c. equal to single stage d. number of stages times of single stage
18. Double tuned amplifiers are used in the following applications [ ]
a. Radio and TV receivers b. Radio and TV transmitters c. Global position systems d. Radar transmitter
19. The gain of double tuned amplifier is compared to a single tuned amplifier [ ]
a. double b. half c. ten times d. same
20. What are the advantages of double tuned amplifier over single tuned amplifier? [ ]
a. smaller bandwidth product and ideal curve characteristics
b. larger gain bandwidth product and ideal curve characteristics
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