ECA
JNTUH OBJECTIVE EXAM
UNIT-1: (SINGLE STAGE AMPLIFIERS)
SECTION-I : Choose the correct answers
1. Which of the following amplifier has high power gain [ b]
(a) CB (b) CE (c) CC (d) both CB and CE
2. The slope of ac load line is _________ that of dc load line. [b ]
(a) same as (b)more than (c) less than (d) None of the above
3. In a RC coupled amplifier, which of the following component is mainly responsible for harmonic distortion of the signal [ a]
(a) Transistor (b) Biasing resistor (c) coupling capacitor (d) power supply
4. The voltage gain of well designed single stage CB amplifier is essentially determined by ac collector load and [C ]
A. Emitter resistor Re B. ac alpha C. Input resistance emitter diode D.ac beta.
5. The emitter of a CE amplifier has no AC voltage because of the [c ]
A. DC voltage unit B. Bypass Capacitor C. Coupling capacitor D. load resistance
6. Typical value of hie is [ ]
A. 1k B. 25k C.50k D.100k
SECTION-II: Fill in the blanks
7. The parameter h22 has units of SEIMENS
8. A CC Amplifier has highest current gain but lowest power gain
9. The current gain of single stage CE amplifier is nearly equal to Beta
10. The input impedance Ri of a CE amplifier in terms of hie, hoe, hre and load resistance. ___________________.
11. The phase difference between output and input voltages of a CB amplifier is 0
12. According to Miller’s theorem, the feedback capacitance when referred to input side with gain A is _Cin = C(1-A)
13. Trans conductance gm in hybrid - π model is defined as gm = ΔIc / ΔVBE when VCE=Constant
UNIT-2: (Multi stage amplifiers)
1. The most desirable feature of transformer coupling is its [c]
A. Higher voltage gain B. wide frequency range C.ability to provide impedance matching D. ability to eliminate hum from the output
2. For matching a circuit of output impedance 200Ω with a load of 8 Ω the turn ratio of the two winding transformer should be [d ]
A. 25 B.1/25 C.1/5 D.5
3. In the initial stages of a multi stage amplifier, we use [a ]
(a) RC coupling (b) transformer coupling (c) direct coupling (d) None
4. The bandwidth of a single stage amplifier is ___ that of a multi stage amplifier. [ a ]
(a) more than (b) less than (c) same as (d) none
5. The Darlington pair consists of the following two stages [ d ]
(a) CE,CC (b)CE,CB (c)both CE (d) both CC
6. Transformer coupling is generally used when RL is Small
7. In a two stage cascaded amplifier, each of two cascaded stages has a voltage gain of 30 then the overall gain is _900
8. Why do we go for multi stage amplifiers? for high gain
9. Direct coupled amplifiers are especially suited for amplifying extremely LOW frequency signals.
10. The DC resistance of transformer coupling is Low so it is more efficient
UNIT-3 (BJT amplifiers-frequency response)
1. The gain bandwidth product of a two stage amplifier is [ c ]
(a) same as that of single stage (b) greater than that of single stage
(c) less than that of single stage (d) product of two gain bandwidth products of each stage
2. How does the amplifier behave for high frequencies? [ b ]
(a) high pass filter (b) low pass filter (c) band pass filter (d) None
3. The bandwidth of an amplifier can be increased by [b ]
A. decreasing the capacitance of its bypass capacitors B.minimizing the stray capacitance
C.increasing the input signal frequency D. cascading it
4. Lower cutoff frequency of an amplifier is primarily determined by the [D ]
A.Internal capacitance of the active device
B.Stray capacitance between its wiring and ground
C.ac beta(β) value of its active devices
D.Capacitances of coupling and bypass capacitor
5. The main reason for the variation of amplifier gain with frequency is [A ]
A. the presence of capacitance internal and external B. due to interstage transformation
C. the logarithmic increase in its output power D. miller effect
6. The alpha (α) cut off frequency of a transistor is higher than is beta (β) cut-off frequency
7. The alpha (α) of the transistor Decreases with the increase in frequency
UNIT-IV (MOS amplifiers)
1. A source follower using FET usually has a voltage gain of _____. [b ]
(a) -1 (b) >100 (c) about -10 (d) less than 1 but positive
2. For the operation of enhancement only N- Channel MOSFET , value of gate voltage has to be [ a]
A. High positive B. high negative C. low positive D. zero
3. In depletion mode and N- Channel DE MOSFET conducts with Vgs is ZERO
4. A MOSFET can be easily destroyed by any Stray voltage on its gate.
5. The positive gate operation of a N- Channel Depletion MOSFET is known as Enhancement mode.
6. Cascade amplifier is combination of CB-CE
7. CD amplifieris called as source follower
8. CS amplifier produces a phase shift of 180˚
Prepared By
KAVITHA