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.
| 1. |
In the diode circuit shown in figure the diodes are ideal. The impedance seen by source is |
| Answer» Only one diode conducts at one time. | |
| 2. |
Figure is a 24 V stabilized power supply. The zener is 24 V, 600 mW. The minimum zener current is 10 mA. Proper values R and maximum load current are |
| Answer» Max. zener current = . Maximum load current = 25 - 10 = 15 mA. | |
| 3. |
The open loop gain of an amplifier is 200. If negative feedback with β = 0.2 is used, the closed loop gain will be |
| Answer» Closed loop gain = . | |
| 4. |
In a class C power amplifier the input signal has a frequency of 250 kHz. If the collector current pulses are 0.1 μs wide, the duty cycle of current waveform is |
| Answer» | |
| 5. |
A full wave rectifier circuit using centre tapped transformer and a bridge rectifier are fed at 100 V, 50 Hz. The frequencies of outputs in these two rectifiers are |
| Answer» Output wave in each case has two cycles for one cycle of input wave. | |
| 6. |
When the ac base voltage in a CE amplifier circuit is too high, the ac emitter current is |
| Answer» A high signal causes distortion because v-i characteristics of BJT is non-linear. | |
| 7. |
In a self bias circuit for CE amplifier, an increase in emitter resistance R results in |
| Answer» Emitter voltage is the same. Increase of emitter resistance decreases with emitter current. | |
| 8. |
In the CE circuit shown in figure the slope of ac load line will be |
| Answer» . | |
| 9. |
When the circuit is switched on, the loop gain of a Wien bridge oscillator is |
| Answer» The initial loop gain must be more than 1. | |
| 10. |
The op-amp circuit shown in the figure is a filter. The type of filter and its cut off type of filter and its cut off frequency are respectively. |
| Answer» At 1000 Hz frequency, Hence, high pass filter, . | |
| 11. |
In figure as the load resistance is changed |
| Answer» Output voltage = 12 V, . | |
| 12. |
In figure, voltage across R = + 10 V. If V = 0.7 V and V = 0.7 V and R = 10 kΩ, current through R is |
| Answer» | |
| 13. |
In a capacitor filter, the time constant RC should be small. |
| Answer» Time constant should be large. | |
| 14. |
A dc power supply has no load voltage of 30 V and full load voltage of 25 V at full load current of 1 A. The output resistance and voltage regulation respectively are |
| Answer» . | |
| 15. |
The main advantage of CC amplifier is |
| Answer» Therefore, it is suitable for impedance matching. | |
| 16. |
If = 0.995, I = 10 mA, I = 0.5 mA, then I will be |
| Answer» . | |
| 17. |
In a negative feedback amplifier A = 100, β = 0.04 and V = 50 mV, then feedback will be |
| Answer» Feed back factor (βA) = 4. | |
| 18. |
An increase in ambient temperature means that maximum power rating of transistor |
| Answer» Increase of ambient temperature means that heat dissipation is slower. | |
| 19. |
Two CE stages are coupled through a capacitor. To calculate the quiescent base current of the two transistors, the capacitor is treated as |
| Answer» Capacitor has infinite impedance for dc. | |
| 20. |
If it is desired to have low output impedance in an amplifier circuit then we should use |
| Answer» Therefore CC configuration is used for impedance matching. | |
| 21. |
A 741 type op-amp has a gain bandwidth product of 1 MHz. A non-inverting amplifier using this op-amp and having a voltage gain of 20 dB will exhibit a -3dB bandwidth of |
| Answer» As we know, Gain Bandwidth, Product = β x A 106 = β x A 20 log A = 20 A = 10' 10 β = 100 kHz. | |
| 22. |
In a full wave rectifier circuit using centre tapped transformer, the peak voltage across half the secondary winding is 40 V. If diodes are ideal, the average output voltage is |
| Answer» . | |
| 23. |
In the circuit of figure, PIV can be up to |
| Answer» Peak inverse voltage can be upto 2Em since capacitor can store charge equal to Em. | |
| 24. |
In the circuit of figure both diodes are ideal. If = 10 V and = 10 V which diode will conduct? |
| Answer» Both D1 and D2 are forward biased. | |
| 25. |
The output impedance of an ideal op-amp is |
| Answer» An ideal op-amp has zero output impedance and can deliver any amount of load current without any voltage drop. | |
| 26. |
In the circuit of the given figure, assume that the diodes are ideal and the meter is an average indicating ammeter, the ammeter will read |
| Answer» Ammeter will real during +ve half cycle only and . | |
| 27. |
A virtual ground is a ground for |
| Answer» No current can flow through virtual ground. However voltage is zero. | |
| 28. |
If the differential voltage gain and the common mode voltage gain of a differential amplifier are 48 dB and 2 dB respectively, then its common mode rejection ratio is |
| Answer» We know that CMMR = 20 log (CMMR) = 20 log Ad - 20 log Ac = 48 - 2 46 dB. | |
| 29. |
A 120 V, 30 Hz source feeds a half wave rectifier circuit through a 4 : 1 step down transformer, the average output voltage is |
| Answer» . | |
| 30. |
The slew rate of an ideal op-amp is |
| Answer» Slew rate signifies the fastest change which can occurs in output voltage. In an ideal op-amp the output can change instantaneously. | |
| 31. |
Regulation of the DC power supply of 12 V, 100 mA is the effective resistance of power supply is 20 Ω |
| Answer» . | |
| 32. |
As compared to a full wave diode rectifier circuit using centre tapped transformer, the bridge diode rectifier circuit has the main advantage of |
| Answer» For bridge rectifier, peak inverse voltage is equal to peak value of ac voltage while for the circuit using centre tapped transformer peak inverse voltage is 2 Em. | |
| 33. |
The units of transistor parameters and are the same. |
| Answer» The units of h11 are ohms and units of h22 siemens. | |
| 34. |
A circuit using an op-amp is shown in the given figure. It has |
| Answer» From above mathematical expression Feedback current If is proportional to V0. So it is a voltage shunt feedback. | |
| 35. |
An oscillator requires an amplifier |
| Answer» Positive feedback is necessary for sustained oscillations. | |
| 36. |
A full wave bridge diode rectifier uses diodes having forward resistance of 50 ohms each. The load resistance is also 50 ohms. The voltage regulations is |
| Answer» No load output voltage = Output voltage at full load = | |
| 37. |
The disadvantage of direct coupled amplifiers is |
| Answer» The drift is amplified by different stages. | |
| 38. |
Positive feedback is mainly used in |
| Answer» In oscillators, the oscillations are generated due to positive feedback. In thyristors anode current increases due to positive feedback. | |
| 39. |
For a BJT if β = 50, I = 3 μA and I = 1.2 mA then I |
| Answer» . | |
| 40. |
The main application of enhancement mode MOSFET is in |
| Answer» Because of high switching speed MOSFET is very suitable for digital circuit. | |
| 41. |
A transistor has a power rating of 8 W for a case temperature of 25°C. If derating factor is 30 mW/°C, the power rating for 55°C, case temperature is |
| Answer» Power rating = 8 - (55 - 25)(30 x 10-3) = 7.1 W. | |
| 42. |
In figure V = 0.7 V. The base current is |
| Answer» | |
| 43. |
An ideal power supply has |
| Answer» An ideal power supply should have zero voltage drop. | |
| 44. |
In the circuit figure LED will be on when is |
| Answer» Voltage input to inverting input is . Therefore, vi should be more than 6 V. | |
| 45. |
A differential amplifier consists of two CB amplifiers. |
| Answer» It consists of two CE amplifiers. | |
| 46. |
A non-inverting op-amp summer is shown in figure, the output voltage V is |
| Answer» I/p voltage = -1 + 1 + sin ωt sin ωt . | |
| 47. |
A 12 kHz pulse wave-form is amplified by a circuit having an Upper cut-off frequency of 1 MHz. The minimum input pulse width that can be accurately reproduced is |
| Answer» tr = 10% Pω = minimum Power(P) = 10 tr 10 x 0.35 μ sec = 3.5 μ sec. Note: The I/P Pulse will be severely distorted if the rise time is more than 10% of Pulse width. | |
| 48. |
Feedback factor may be less or more than 1. |
| Answer» Feedback factor is much less than 1. | |
| 49. |
An RC oscillator uses |
| Answer» One RC combination can give a phase shift of less them 90°. Therefore 3 RC combinations are required for 180° phase shift. | |
| 50. |
The main advantage of CMOS circuit is |
| Answer» Low power consumption is a big advantage in digital circuits. | |