264 + Interview Questions in Analog Electronics in Electronics and Communication Engineering Page 5 InterviewSolution

201.	The purpose of connecting a coupling capacitor in the output circuit of an amplifier is
Answer» Capacitor acts for ac or dc.

Discussion

202.	Generally the gain of a transistor amplifier falls at high frequencies due to the
Answer» At high frequency, internal capacitance comes into consideration.

Discussion

203.	The open loop gain of an actual op-amp is about 100.
Answer» It is very high.

Discussion

204.	If the Q of a single stage single tuned amplifier is doubled, the bandwidth will
Answer» . If Q is doubles, bandwidth becomes half.

Discussion

205.	In full wave rectification, if the input frequency is 50 Hz, then frequency at the output of filter is
Answer» Filter output will give d.c. signal and d.c. signal Passed zero frequency.

Discussion

206.	A CB amplifier has = 0.98 and R = 600 &ohm;. If I = 3.5 mA, the current gain is
Answer» Current gain of CB amplifier is a.

Discussion

207.	of an op-amp is about 1 kHz.
Answer» It is about 1 MHz.

Discussion

208.	In figure, D turns on when
Answer» D1 is forward biased when vi > V1.

Discussion

209.	In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half of the secondary winding is 30 V. Then PIV is
Answer» In full wave circuit using centre tapped transformer PIV = 2Vm .

Discussion

210.	A voltage tripler circuit and voltage quadrupler circuit use identical components. Then
Answer» Since voltage quadrupler circuit uses more components, voltage drop will be more and voltage regulation poorer.

Discussion

211.	A Ge diode operated at a junction temperature of 27°C. For a forward current of 10 mA, V is found to be 0.3 V. If V = 0.4 V then forward current will be
Answer» iD2 = (47.73) x 10 mA = 466 mA.

Discussion

212.	The turn ratio of a transformer is 20:1, if a load of 10&ohm; is connected across the secondary, what will be the effective resistance seen looking into the Primary?
Answer»

Discussion

213.	In a CE amplifier circuit the ac voltage between emitter and ground
Answer» Common emitter means emitter at ground potential.

Discussion

214.	An amplifier has input impedance of 4 k&ohm; and output impedance of 80 k&ohm;. It is used in negative feedback circuit with 10% feedback. If open loop gain is 90, the closed loop input and output impedances are
Answer» Closed loop input impedance = 4 (1 + 0.1 x 90) = 40 k&ohm;, Closed loop Output impedance = = 8 k&ohm;.

Discussion

215.	In figure the current through resistor R
Answer» .

Discussion

216.	Voltage V in the circuit when V < 0 where D is an ideal diode. (Take R = R = R = 1 &ohm;)
Answer» if Vs ≥ 0, then id ≥ 0 if Vs < 0 then id < 0, Diode D is replaced by and open ckt and id = 0, hence VL = id . RL = 0.

Discussion

217.	A bridge rectifier circuit has a dc load current of 10 mA and a filter capacitance of 1000 μF. The peak to peak ripple voltage is
Answer» Peak to peak ripple voltage = .

Discussion

218.	In the circuit of figure, the value of is (neglecting )
Answer» .

Discussion

219.	Figure uses 10 V zener diode. The minimum and maximum current through series resistance are
Answer» Minimum current = = 10 mA. Minimum current = = 30 mA.

Discussion

220.	In a power amplifier the collector current flows for 270° of the input cycle. The operations is
Answer» In class A operation IC exists for 360°. In class B operation IC exists for 180°. In between there is the class AB.

Discussion

221.	When load is coupled to class A amplifier through transformer, efficiency decreases.
Answer» Transformer coupling increases efficiency.

Discussion

222.	The gain of an FET amplifier can be changed by changing
Answer» Gain is proportional to gm .

Discussion

223.	To prevent a DC return between source and load, it is necessary to use
Answer» Capacitor offers infinite impedance to DC.

Discussion

224.	For a base current of 10 μA, what is the value of collector current in common emitter if β = 100
Answer» IC = 10 x 100 μA = 1 mA.

Discussion

225.	If the input to the ideal comparator shown in the figure is a sinusoidal signal of 8 V (peak to peak) without any DC component, then the output of the comparator has a duty cycle of
Answer»

Discussion

226.	In figure The minimum and maximum load currents are
Answer» When RL = ∞, IL = 0, When RL = 100 &ohm;, or 120 mA.

Discussion

227.	In figure, V = 0.6 V, β = 99. Then V and I are
Answer» VC = 20 - 1.98 x 10-3 x 5.4 x 103 9.3 V.

Discussion

228.	The input impedance of op-amp circuit of figure is
Answer» Due to the presence of virtual ground at input, the resistance in the series path of input of inverting amplifier is input impedance.

Discussion

229.	In a BJT circuit a transistor is replaced by transistor. To analyse the new circuit
Answer» All voltages and currents have reverse polarity.

Discussion

230.	To protect the diodes in a rectifier and capacitor input filter circuit it is necessary to use
Answer» Resistor reduces surge current.

Discussion

231.	In the amplifier circuit of figure = 100 and = 1000 &ohm;. The voltage gain of amplifier is about
Answer» .

Discussion

232.	The efficiency of a full wave rectifier using centre tapped transformer is twice that in full wave bridge rectifier.
Answer» Efficiency of full wave rectifier with centre tapped transformer is slightly higher than that of bridge rectifier.

Discussion

233.	Negative feedback reduces noise originating at the amplifier input.
Answer» It has no effect on noise originating at amplifier input.

Discussion

234.	The output V in figure is
Answer» Input to non-inverting op-amp is -10 x 10-6 x 103 = -10 mV. Therefore output = = -100 mV.

Discussion

235.	In a CE amplifier the input impedance is equal to the ratio of
Answer» Input is applied to base with emitter grounded. The input impedance is the ratio of ac base voltage to ac base current.

Discussion

236.	For a system to work, as oscillator the total phase shift of the loop gain must be equal to
Answer» Gain of system with + ve feedback = for oscillation but V0 ≠ 0 so, that 1 - AB = 0 AB = 1 ∠0° or 360°.

Discussion

237.	An amplifier has a large ac input signal. The clipping occurs on both the peaks. The output voltage will be nearly a
Answer» When a sinusoidal voltage is clipped on both sides it resembles a square wave.

Discussion

238.	A CB amplifier has = 6 &ohm;, R = 600 &ohm; and = 0.98. The voltage gain is
Answer»

Discussion

239.	A bridge rectifier circuit has input of 50 Hz frequency. The load resistance is R and filter capacitance is C. For good output wave shape, the time constant RC should be at least equal to
Answer» Time constant RLC must be about 5 x 20 ms.

Discussion

240.	Maximum efficiency of class B power amplifier is 50%.
Answer» Maximum efficiency for class B-operation can be 78.5% .

Discussion

241.	In figure what is the base current if V = 0.7 V
Answer» .

Discussion

242.	In figure I = 4 mA. Then V =
Answer» VS = ISRS = 4 x 10-3 x 1.1 x 103 = 4.4 V.

Discussion

243.	The self bias provides
Answer» Stable Q point is the advantage of self bias circuit.

Discussion

244.	In figure what is value of I if β = 100. Neglect V
Answer» Since IB = 100 μA, IC = βIB = 10 mA.

Discussion

245.	In figure the saturation collector current is
Answer» Since IE IC, .

Discussion

246.	In figure = 8 V and = 8 V. Which diode will conduct?
Answer» Both D1 and D2 are forward biased.

Discussion

247.	A forward voltage of 9 V is applied to a diode in series with a 1 k&ohm; load resistor. The voltage across load resistor is zero. It indicates that
Answer» Since load voltage is zero, the current is zero and diode is open-circuited. If load was open-circuited, load voltage would be about 9 V.

Discussion

248.	Which power amplifier can deliver maximum load power?
Answer» Since efficiency of class C operation is high, maximum load power is delivered.

Discussion

249.	In class C operation of an amplifier circuit, the collector current exists for
Answer» In class C operation output is in the form of short duration pulses.

Discussion

250.	The '' parameters of the circuit shown in the figure are = 25 &ohm;, = 0.999 and = 10&ohm; The Voltage gain is
Answer» Zi = 25 + 10-6 x 0.99 x 104 25 .

Discussion

Explore topic-wise InterviewSolutions in .

The purpose of connecting a coupling capacitor in the output circuit of an amplifier is

Generally the gain of a transistor amplifier falls at high frequencies due to the

The open loop gain of an actual op-amp is about 100.

If the Q of a single stage single tuned amplifier is doubled, the bandwidth will

In full wave rectification, if the input frequency is 50 Hz, then frequency at the output of filter is

A CB amplifier has = 0.98 and R = 600 &ohm;. If I = 3.5 mA, the current gain is

of an op-amp is about 1 kHz.

In figure, D turns on when

In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half of the secondary winding is 30 V. Then PIV is

A voltage tripler circuit and voltage quadrupler circuit use identical components. Then

A Ge diode operated at a junction temperature of 27°C. For a forward current of 10 mA, V is found to be 0.3 V. If V = 0.4 V then forward current will be

The turn ratio of a transformer is 20:1, if a load of 10&ohm; is connected across the secondary, what will be the effective resistance seen looking into the Primary?

In a CE amplifier circuit the ac voltage between emitter and ground

An amplifier has input impedance of 4 k&ohm; and output impedance of 80 k&ohm;. It is used in negative feedback circuit with 10% feedback. If open loop gain is 90, the closed loop input and output impedances are

In figure the current through resistor R

Voltage V in the circuit when V < 0 where D is an ideal diode. (Take R = R = R = 1 &ohm;)

A bridge rectifier circuit has a dc load current of 10 mA and a filter capacitance of 1000 μF. The peak to peak ripple voltage is

In the circuit of figure, the value of is (neglecting )

Figure uses 10 V zener diode. The minimum and maximum current through series resistance are

In a power amplifier the collector current flows for 270° of the input cycle. The operations is

When load is coupled to class A amplifier through transformer, efficiency decreases.

The gain of an FET amplifier can be changed by changing

To prevent a DC return between source and load, it is necessary to use

For a base current of 10 μA, what is the value of collector current in common emitter if β = 100

If the input to the ideal comparator shown in the figure is a sinusoidal signal of 8 V (peak to peak) without any DC component, then the output of the comparator has a duty cycle of

In figure The minimum and maximum load currents are

In figure, V = 0.6 V, β = 99. Then V and I are

The input impedance of op-amp circuit of figure is

In a BJT circuit a transistor is replaced by transistor. To analyse the new circuit

To protect the diodes in a rectifier and capacitor input filter circuit it is necessary to use

In the amplifier circuit of figure = 100 and = 1000 &ohm;. The voltage gain of amplifier is about

The efficiency of a full wave rectifier using centre tapped transformer is twice that in full wave bridge rectifier.

Negative feedback reduces noise originating at the amplifier input.

The output V in figure is

In a CE amplifier the input impedance is equal to the ratio of

For a system to work, as oscillator the total phase shift of the loop gain must be equal to

An amplifier has a large ac input signal. The clipping occurs on both the peaks. The output voltage will be nearly a

A CB amplifier has = 6 &ohm;, R = 600 &ohm; and = 0.98. The voltage gain is

A bridge rectifier circuit has input of 50 Hz frequency. The load resistance is R and filter capacitance is C. For good output wave shape, the time constant RC should be at least equal to

Maximum efficiency of class B power amplifier is 50%.

In figure what is the base current if V = 0.7 V

In figure I = 4 mA. Then V =

The self bias provides

In figure what is value of I if β = 100. Neglect V

In figure the saturation collector current is

In figure = 8 V and = 8 V. Which diode will conduct?

A forward voltage of 9 V is applied to a diode in series with a 1 k&ohm; load resistor. The voltage across load resistor is zero. It indicates that

Which power amplifier can deliver maximum load power?

In class C operation of an amplifier circuit, the collector current exists for

The '' parameters of the circuit shown in the figure are = 25 &ohm;, = 0.999 and = 10&ohm; The Voltage gain is