InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
A diode can have a very high forward resistance. |
| Answer» Forward resistance of diode is low. | |
| 152. |
The ideal characteristics of a stabilizer is |
| Answer» A stabilizer must give constant output voltage. This is possible only if internal resistance is low. | |
| 153. |
In figure, transistor β = 100 and LED voltage when it is conducting is 2 V. Then the base current which saturates the transistor is |
| Answer» . | |
| 154. |
In figure the dc emitter current of each transistor is about |
| Answer» Total . It divides equally between the two transistors. | |
| 155. |
The input voltage for starting oscillations in an oscillator is caused by |
| Answer» The amplifier in the oscillator amplifies the noise voltages. However phase shift around the closed loop is zero at only one frequency. Therefore, only this frequency appears at output. | |
| 156. |
The current flowing in a certain P-N junction at room temperature is 2 x 10 Amp. When a large reverse biased voltage is applied. Calculate the current flowing when 0.1 volts is applied. |
| Answer» | |
| 157. |
Values of V at 20°C for an ideal P-N diode |
| Answer» . | |
| 158. |
In figure which diode will conduct and what will be the value of V? |
| Answer» Since battery connected to anode of D, is of 5 V it is forward biased. D1 and D3 are reverse biased. Output voltage is 5 V. | |
| 159. |
A CB amplifier has I = 3.5 mA, = 0.98 and R = 600 Ω. The input impedance |
| Answer» . Input impedance of CB amplifier equals re . | |
| 160. |
For the amplifier circuit of figure, the parameters of transistor are = 25 Ω, = 0.999, = 10 Ω. The voltage gain is |
| Answer» It is a common base circuit . | |
| 161. |
In figure, V = + 30 V, R = 200 kΩ and R = 100 kΩ. If V = 0.7 V, the voltage a cross R = |
| Answer» . | |
| 162. |
For the circuit in figure the output wave shape is |
| Answer» It is a biased limiter circuit. During positive half clipping is at 5 V due to battery. | |
| 163. |
In figure V = |
| Answer» . | |
| 164. |
In figure, I = 4 mA. Then V = |
| Answer» VS = 4 x 10-3 x 1.5 x 10-3 = 6 V. | |
| 165. |
For the circuit of figure the critical frequency is |
| Answer» The two resistances are in parallel. Critical frequency = . | |
| 166. |
The current through R is(If β = 99, V = 0.74 V) |
| Answer» IE = 1 mA, VBE = 0.7V, β = 99, IC = aIE, IC = β, IB 1 = IB = 0.01 mA. 0.1 mA. | |
| 167. |
A transistor with = 0.9 and I = 10 μA is biased so that I = 90 μA. Then I will be |
| Answer» IEQ = ICQ + IBQ = 910 μA + 90 μA 990 μA. | |
| 168. |
In a CE amplifier drives a low load resistance directly the result will be |
| Answer» Low load resistance means high current and hence over loading. | |
| 169. |
For CE amplifier of figure, the slope of ac load line is |
| Answer» For ac, RL and RC appear in parallel. Hence . | |
| 170. |
For high frequencies a capacitor like |
| Answer» . If w is very high, XC, is nearly zero. | |
| 171. |
Which component is allowed to pass through it by a choke filter? |
| Answer» XL is zero for dc. | |
| 172. |
In an amplifier the stray capacitances assume impedance at low frequencies |
| Answer» Stray capacitances assume importance at high frequencies because . | |
| 173. |
In CE amplifier the base current is very high. |
| Answer» Base current is small. | |
| 174. |
A transistor has a maximum power dissipation of 350 mW at an ambient temperature of 25°C. If derating factor is 2 mW/°C, the maximum power dissipation for 40°C ambient temperature is |
| Answer» Derating improves reliability but does not affect maximum power dissipation. | |
| 175. |
An amplifier has open loop gain of 100, input impedance 1 kΩ and output impedance 100 Ω. If negative feedback with β = 0.99 is used, the new input and output impedances are |
| Answer» Input impedance with feedback = (1 kΩ) (1 + 100 + 0.99) = 100 kΩ. Output impedance with feedback = . | |
| 176. |
In a BJT amplifier the power gain from base to collector is 4000. The power gain in dB is |
| Answer» Gain in dB = 10 log (4000). | |
| 177. |
In figure, secondary winding has 40 turns. For maximum power transformer to 2 ohm resistance the number of turns in primary is |
| Answer» . | |
| 178. |
The output voltage waveform of a CE amplifier is fed to a dc coupled CRO. The trace on the screen will be |
| Answer» Due to direct coupling between output and CRO both dc and ac output voltage will appear on screen of CRO. | |
| 179. |
In an RC phase shift oscillator, the total phase shift of the three RC lead networks is |
| Answer» Each RC network gives 60° phase shift. | |
| 180. |
In the circuit of figure β = 100 and quiescent value of base current is 20 μA. The quiescent value of collector current is |
| Answer» IC = βIB = 2 mA. | |
| 181. |
In a CE amplifier circuit the dc voltage between emitter and ground |
| Answer» Since dc is flowing through emitter resistance, dc voltage cannot be zero. | |
| 182. |
A buffer amplifier should have |
| Answer» So that it can couple high impedance source to low impedance load and maximum power can be transferred. | |
| 183. |
A second order active bandpass filter can be obtained by cascading LP second order filter having higher cut off frequency with a second order HP filter having lower cut off frequency provided |
| Answer» If fOL is less than fOH, a passband will exist from fOL to fOH . | |
| 184. |
In figure the approximate voltages of |
| Answer» Base voltage = . Emitter voltage = - 8 + 0.7 = - 7.3 V. | |
| 185. |
The open loop gain of an amplifier is 50 but likely to decrease by 20% due to various factors. If negative feedback with β = 0.1 is used, the change in gain will be about |
| Answer» The stabilisation of gain is one of the advantages of closed loop system. | |
| 186. |
In the graphical analysis of CE amplifier circuit, the upper end of load line is called |
| Answer» Current is maximum at saturation point. | |
| 187. |
A full wave rectifier supplies a load of 1 kΩ. The a.c. Voltage applied to the diodes is 220 - 0 - 220 Volts rms. If diode resistance is neglected, then Average d.c. Voltage |
| Answer» . | |
| 188. |
An R-C coupled amplifier has mid-frequency gain of 200 and a frequency response from 100 Hz to 20 kHz. A negative feedback network with β = 0.2 is incorporated into the amplifier circuit, the Bandwidth will be |
| Answer» B.W. = fH' - fL' . | |
| 189. |
A difference amplifier using op-amp has closed loop gain = 50. If input is 2 V to each of inverting and non-inverting terminals, output is 5 mA. Then CMRR = |
| Answer» . | |
| 190. |
The coupling capacitor in amplifier circuits |
| Answer» Capacitor is open-circuit for dc. | |
| 191. |
In figure if C is replaced by short circuit then R will be |
| Answer» If C is short circuited then, by using KCL and KVL, | |
| 192. |
An transistor has a Beta cutoff frequency of 1 MHz, and a common emitter short circuit low frequency current gain β of 200. It unity gain frequency and the alpha cut off frequency respectively are |
| Answer» . | |
| 193. |
In figure if the transistor is cut off, the collector voltage is equal to |
| Answer» Since transistor is cut off, IC = 0 and VC = VCC . | |
| 194. |
If input frequency is 50 Hz, the frequency of output wave in a full wave diode rectifier circuit is |
| Answer» There are two output waves for one input wave. | |
| 195. |
A class A transformer coupled power amplifier is to deliver 10 W output. The power rating of transistor should not be less than |
| Answer» Efficiency is 50%. Therefore input is 20 W. | |
| 196. |
A bridge diode circuit using ideal diodes has in input voltage of 20 sin ω volts. The average and rms values of output voltage are |
| Answer» . | |
| 197. |
In the circuit of figure = 8 V and = 0. Which diode will conduct (Assume ideal diodes)? |
| Answer» Since only v1 is positive and more than 0.7 V only D1 will conduct. | |
| 198. |
For an transistor connected as shown in the figure V = 0.7 volts. Given that reverse saturation current of the junction at room temperature 300K is 10A, the emitter current. |
| Answer» IE = aIE + ICBO and approximated. But a is not given in the question. It is not possible to find. | |
| 199. |
The dc output voltage of the circuit is |
| Answer» This is half wave Rectifier, because in +ve cycle both the diode will be in forward biased. For +ve cycle, Vo max = Imax. Req 2.59 x 10-3 x 1.66 x 103 4.299 volt. | |
| 200. |
A voltage doubler circuit is fed by a voltage V sin ω. The output voltage will be nearly 2 V only if |
| Answer» If load resistance is large, current would be low and voltage drop would be low. | |