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MCQOPTIONS
This section includes 1136 Mcqs, each offering curated multiple-choice questions to sharpen your Electronics & Communication Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 151. |
A potential of 7 V is applied to a silicon diode. A resistance of 1 kΩ is also connected in series. If the diode is forward biased, the current in the circuit is |
| A. | 7 mA |
| B. | 6.3 mA |
| C. | 0.7 mA |
| D. | 0 |
| Answer» C. 0.7 mA | |
| 152. |
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 |
| A. | 20% |
| B. | 2% |
| C. | 0.5% |
| D. | 0.05% |
| Answer» D. 0.05% | |
| 153. |
The open loop gain of an amplifier is 200. If negative feedback with β = 0.2 is used, the closed loop gain will be |
| A. | 200 |
| B. | 40.12 |
| C. | 4.878 |
| D. | 2.2 |
| Answer» D. 2.2 | |
| 154. |
Thermal runaway is not possible in FET because as the temperature of FET increases |
| A. | The mobility decreases |
| B. | The transconductance increases |
| C. | The drain current increases |
| D. | None of the above |
| Answer» B. The transconductance increases | |
| 155. |
The effective channel length of a MOSFET in a saturation decreases with increase in |
| A. | Gate voltage |
| B. | Drain voltage |
| C. | Source voltage |
| D. | Body voltage |
| Answer» C. Source voltage | |
| 156. |
The early effect in a bipolar junction transistor is caused by |
| A. | Fast turn-on |
| B. | Fast turn-off |
| C. | Large collector-base reverse bias |
| D. | Large emitter-base forward bias |
| Answer» D. Large emitter-base forward bias | |
| 157. |
A differential amplifier is invariably used in the i/p stage of all OP-amps.This is dome basically to provide the OP-amps with a very high |
| A. | CMRR |
| B. | Bandwidth |
| C. | Slew rate |
| D. | Open-loop gain |
| Answer» B. Bandwidth | |
| 158. |
A 741-type OP-amp has a gain-bandwidth product of 1MHz.A non-inverting amplifier using this opamp & having a voltage gain of 20db will exhibit -3db bandwidth of |
| A. | 50 KHz |
| B. | 100 KHz |
| C. | 1000/17 KHz |
| D. | 1000/7.07 KHz |
| Answer» C. 1000/17 KHz | |
| 159. |
Class AB operation is often used in power large signal) amplifiers in order to |
| A. | Get maximum efficiency |
| B. | Remove even harmonics |
| C. | Overcome a crossover distortion |
| D. | Reducing collector dissipation |
| Answer» D. Reducing collector dissipation | |
| 160. |
A dc power supply has no-load voltage of 30v,and a full-load voltage of 25v at full-load current of 1A.Its output resistance & load regulation ,respectively are |
| A. | 5 Ω & 20 % |
| B. | 25 Ω & 20 % |
| C. | 5 Ω & 16.7 % |
| D. | 25 Ω & 16.7 % |
| Answer» C. 5 Ω & 16.7 % | |
| 161. |
Three identical amplifiers with each one having a voltage gain of 50,input resistance of 1KΩ & output resistance of 250, are cascaded. The open circuit voltage gain of combined amplifier is |
| A. | 49dB |
| B. | 51dB |
| C. | 98dB |
| D. | 102dB |
| Answer» D. 102dB | |
| 162. |
Asource follower using an FET usually has a voltage gain which is |
| A. | Greater than +100 |
| B. | Slightly less than unity but positive |
| C. | Exactly unity but negative |
| D. | About -10 |
| Answer» B. Slightly less than unity but positive | |
| 163. |
MOSFET can be used as a |
| A. | Current controlled capacitor |
| B. | Voltage controlled capacitor |
| C. | Current controlled inductor |
| D. | Voltage controlled inductors |
| Answer» C. Current controlled inductor | |
| 164. |
Voltage Series (feedback also called series-shunt feedback) results in |
| A. | Increase in both input & output impedances |
| B. | Decreases in both input & output impedances |
| C. | Increase in input impedance & decreases in output impedance |
| D. | Decrease in input impedance & increase in output impedance |
| Answer» D. Decrease in input impedance & increase in output impedance | |
| 165. |
An amplifier using an opamp with slew rate SR=1v/µsec has a gain of 40db.if this amplifier has to faithfully amplify sinusoidal signals from dc to 20 KHz without introducing any slew-rate induced distortion, then the input signal level must not exceed |
| A. | 795mV |
| B. | 395mV |
| C. | 79.5 mV |
| D. | 39.5mV |
| Answer» D. 39.5mV | |
| 166. |
Generally, 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 |
| Answer» B. Coupling capacitor at the input | |
| 167. |
The current gain of a bipolar transistor drops at high frequencies because of |
| A. | Transistor capacitances |
| B. | High current effects in the base |
| C. | Parasitic inductive elements |
| D. | The early effect |
| Answer» B. High current effects in the base | |
| 168. |
Most of the linear ICs are based on the two-transistor differential amplifier because of its |
| A. | Input voltage dependent linear transfer characteristic |
| B. | High voltage gain |
| C. | High input resistance |
| D. | High CMRR |
| Answer» E. | |
| 169. |
The MOSFET switch in its onstate may be considered equivalent to |
| A. | Resistor |
| B. | Inductor |
| C. | Capacitor |
| D. | Battery |
| Answer» D. Battery | |
| 170. |
Introducing a resistor in the emitter of a common amplifier stabilizes the dc operating point against variations in |
| A. | Only the temperature |
| B. | only the β of the transistor |
| C. | Both Temperature & β |
| D. | None of the above |
| Answer» D. None of the above | |
| 171. |
The bandwidth of an RF tuned amplifier is dependent on |
| A. | Q –factor of the tuned o/p circuit |
| B. | Q –factor of the tuned i/p circuit |
| C. | Quiescent operating point |
| D. | Q-factor of the o/p and i/p circuits as well as quiescent operating point |
| Answer» B. Q –factor of the tuned i/p circuit | |
| 172. |
A change in the value of the emitter resistance Re in a differential amplifier |
| A. | Affects the difference mode gain Ad |
| B. | Affects the common mode gain Ac |
| C. | Affects both Ad and Ac |
| D. | Does not effect either Ad and Ac |
| Answer» C. Affects both Ad and Ac | |
| 173. |
The current gain of a BJT is |
| A. | gm r0 |
| B. | gm / r0 |
| C. | gm rπ |
| D. | gm /rπ |
| Answer» D. gm /rπ | |
| 174. |
In a common emitter, unbypassed resister provides |
| A. | voltage shunt feedback |
| B. | current series feedback |
| C. | negative voltage feedback |
| D. | positive current feedback |
| Answer» D. positive current feedback | |
| 175. |
An n- channel JFET has IDSS=2mA,and Vp=-4v.Its transconductance gm=in mA/V)for an applied gate to source voltage VGS=-2v is |
| A. | 0.25 |
| B. | 0.5 |
| C. | 0.75 |
| D. | 1 |
| Answer» C. 0.75 | |
| 176. |
The most commonly used amplifier in sample & hold circuits is |
| A. | A unity gain non-inverting amplifier |
| B. | A unity gain inverting amplifier |
| C. | An inverting amplifier with a gain of 10 |
| D. | An inverting amplifiers with a gain of 100 |
| Answer» C. An inverting amplifier with a gain of 10 | |
| 177. |
An amplifier without feedback has a voltage gain of 50,input resistance os 1 KΩ & Output resistance of 2.5KΩ.The input resistance of the current shunt negative feedback amplifier using the above amplifier with a feedbacik factor of 0.2 is |
| A. | 1/11KΩ |
| B. | 1/5KΩ |
| C. | 5KΩ |
| D. | 11KΩ |
| Answer» B. 1/5KΩ | |
| 178. |
An npn BJT has gm=38mA/v, cµ =10¯14 F, cπ =10¯13F and DC current gain β0=90.For this transistor fT & fβ are |
| A. | fT =1.64 x 108 Hz & fβ = 1.47 x 1010 Hz |
| B. | fT =1.47 x 1010 Hz & fβ = 1.64 x 108 Hz |
| C. | fT =1.33 x 1012 Hz & fβ = 1.47 x 1010 Hz |
| D. | fT =1.47 x 1010 Hz & fβ = 1.33 x 1012 Hz |
| Answer» C. fT =1.33 x 1012 Hz & fβ = 1.47 x 1010 Hz | |
| 179. |
The cascade amplifier is a multistage configuration of |
| A. | CC-CB |
| B. | CE-CB |
| C. | CB-CC |
| D. | CE-CC |
| Answer» C. CB-CC | |
| 180. |
Which of the following is not associated with a p-n junction |
| A. | Junction capacitance |
| B. | Charge storage capacitance |
| C. | Depletion capacitance |
| D. | Channel length modulation |
| Answer» E. | |
| 181. |
If=0.98, Ico=6µA and Iβ=100µA for a transistor,then the value of Ic will be |
| A. | 2.3mA |
| B. | 3.2mA |
| C. | 4.6mA |
| D. | 5.2mA |
| Answer» E. | |
| 182. |
A constant current signal across a parallel RLC circuits gives an o/p of 1.4v at the signal frequency of 3.89KHZ and 4.1KHZ. At the frequency of 4KHZ,the o/p voltage will be |
| A. | 1v |
| B. | 2v |
| C. | 1.4v |
| D. | 2.8v |
| Answer» C. 1.4v | |
| 183. |
In a p⁺n junction diode under reverse bias , the magnitude of electric field is maximum at |
| A. | The edge of the depletion region on the p-side |
| B. | The edge of the depletion region on the n-side |
| C. | The p⁺n junction |
| D. | The center of the depletion region on the n-side |
| Answer» D. The center of the depletion region on the n-side | |
| 184. |
The action of JFET in its equivalent circuit can best be represented as a |
| A. | Current controlled Current source |
| B. | Current controlled voltage source |
| C. | Voltage controlled voltage source |
| D. | voltage controlled current source |
| Answer» E. | |
| 185. |
Consider the following rectifier circuits : half-wave rectifier without filterfull-wave rectifier without filterfull-wave rectifier with series inductance filterfull-wave rectifier with capacitance filter. The sequence of these rectifier circuits in decreasing order of their ripple factor is |
| A. | 1, 2, 3, 4 |
| B. | 3, 4, 1, 2 |
| C. | 1, 4, 3, 2 |
| D. | 3, 2, 1, 4 |
| Answer» B. 3, 4, 1, 2 | |
| 186. |
The transformer cores operating at microwave frequency ranges are generally made up of |
| A. | silicon steel |
| B. | ferrites |
| C. | albino |
| D. | super alloy |
| Answer» C. albino | |
| 187. |
The absolute values of pinch-off voltage and gate-source cut-off voltage are |
| A. | nearly zero |
| B. | complementary to each other |
| C. | never equal |
| D. | equal |
| Answer» E. | |
| 188. |
A FET is a __________ controlled device whereas a bipolar transistor is a __________ controlled device. |
| A. | gate, drain |
| B. | drain, gate |
| C. | current, voltage |
| D. | voltage, current |
| Answer» E. | |
| 189. |
In a CE amplifier the ac cut off voltage is 9 V and slope of ac load line is - 0.5 mA/V. The ac saturation current is |
| A. | 9 mA |
| B. | 4.5 mA |
| C. | 3 mA |
| D. | 18 mA |
| Answer» C. 3 mA | |
| 190. |
When the emitter current of a transistor is changed by 1 mA, its collector current changes by 0.990 mA. The common base short circuit current gain a for the transistor is |
| A. | 0.99 |
| B. | 1.01 |
| C. | 1.001 |
| D. | 0.99 |
| Answer» B. 1.01 | |
| 191. |
In applications where __________ input resistance is needed, the JFET is preferred to the bipolar transistor. |
| A. | zero |
| B. | very low |
| C. | low |
| D. | high |
| Answer» E. | |
| 192. |
In figure, VCC = + 30 V, R1 = 200 kΩ and R2 = 100 kΩ. If VBE = 0.7 V, the voltage a cross RE = |
| A. | +20 V |
| B. | +19.3 V |
| C. | +10 V |
| D. | +9.3 V |
| Answer» E. | |
| 193. |
In amplifiers, the parasitic oscillation result due to |
| A. | transistor inter junction capacitance |
| B. | push pull operator |
| C. | negative feedback |
| D. | poor inter-stage coupling |
| Answer» B. push pull operator | |
| 194. |
Assertion (A): The main use of positive feedback is in oscillator circuits.Reason (R): In an oscillator the loop gain Aβ is kept slightly more than unity |
| A. | Both A and R are correct and R is correct explanation for A |
| B. | Both A and R are correct but R is not correct explanation for A |
| C. | A is correct R is wrong |
| D. | A is wrong R is correct |
| Answer» C. A is correct R is wrong | |
| 195. |
Which of the following figures is an ideal equivalent circuit of a n-p-n transistor? |
| A. | figure A |
| B. | figure B |
| C. | figure C |
| D. | none |
| Answer» C. figure C | |
| 196. |
Rise time in a transistor is change from |
| A. | 10% of its final value to 100% of its final value |
| B. | 10% to its final value to 50% of its final value |
| Answer» B. 10% to its final value to 50% of its final value | |
| 197. |
Which of the following are synonymous? |
| A. | MOSFET and IGEFT |
| B. | FET and JFET |
| C. | JFET and MOSFET |
| D. | P-N-P and N-P-N |
| Answer» B. FET and JFET | |
| 198. |
A CB amplifier has IE = 3.5 mA, a = 0.98 and RL = 600 Ω. The input impedance |
| A. | 0.98 Ω |
| B. | 0.025 Ω |
| C. | |
| Answer» D. | |
| 199. |
To obtain very high I/P and O/P impedances in a feedback amplifier, the topology used is |
| A. | voltage series |
| B. | current series |
| C. | voltage shunt |
| D. | current shunt |
| Answer» D. current shunt | |
| 200. |
An op-amp uses |
| A. | RC coupling |
| B. | direct coupling |
| C. | transformer coupling |
| D. | either (b) or (c) |
| Answer» C. transformer coupling | |