📡 Electronics and Communication Engineering (ECE) Solved MCQs with Answers

Practice 406 approved 📡 Electronics and Communication Engineering (ECE) questions with verified answers from the 🛠️ Engineering Essentials subject for Pakistan exams.

406 solved MCQs

As compared to an ordinary semiconductor diode, a Schottky diodeAnswer: has lower cut in voltage Assertion (A): When a high reverse voltage is applied to a p-n junction the diode breaks down. Reason (R): High reverse voltage causes Avalanche effect.Answer: Both A and R are true and R is correct explanation of A As compared to an ordinary semiconductor diode, a Schottky diodeAnswer: has higher reverse saturation current and lower cut in voltage Crossover distortion behaviour is characteristic ofAnswer: class B O/P stage If aac for transistor is 0.98 then βac is equal toAnswer: 49 Assertion (A): The conductivity of p type semiconductor is higher than that of intrinsic semiconductor. Reason (R): The addition of donor impurity creates additional energy levels below conduction band.Answer: Both A and R are true but R is not a correct explanation of A In an n-p-n transistor biased for operation in forward active regionAnswer: base is positive with respect to emitter and collector is positive with respect to base An increase in temperature increases the width of depletion layer.Answer: False A zener diode is used inAnswer: voltage regulator circuit In a zener diodeAnswer: sharp breakdown occurs at a certain reverse voltage In a bipolar transistor which current is largestAnswer: emitter current Secondary emission is always decremental.Answer: False In a degenerate n type semiconductor material, the Fermi level,Answer: is in conduction band The types of carriers in a semiconductor areAnswer: 2 A potential of 7 V is applied to a silicon diode. A resistance of 1 K ohm is also in series with the diode. The current isAnswer: 6.3 mA Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C. Reason (R): The reverse saturation current in a semiconductor diode doubles for every 10°C rise in temperature.Answer: Both A and R are true and R is correct explanation of A A periodic voltage has following value for equal time intervals changing suddenly from one value to next... 0, 5, 10, 20, 50, 60, 50, 20, 10, 5, 0, -5, -10 etc. Then rms value of the waveform isAnswer: 31 V Work function of oxide coated cathode is much lower than that of tungsten cathode.Answer: True The word enhancement mode is associated withAnswer: MOSFET In which region of a CE bipolar transistor is collector current almost constant?Answer: Active region A p-n junction diode hasAnswer: all of the above Which of the following is true as regards photo emission?Answer: Maximum velocity of electron increases with decreasing wave length The power dissipation in a transistor is the product ofAnswer: collector current and collector to emitter voltage The normal operation of JFET isAnswer: constant current region In a parallel resonant circuit, the circuit current at resonance is maximum.Answer: False An RLC series circuit is underdamped. To make it overdamped, the value of RAnswer: has to be increased Henry is equivalent toAnswer: Weber/Ampere In a minimum functionAnswer: the degree of numerator and denominator are equal For a transmission line open circuit and short circuit impedances are 20 Ω and 5 Ω. Then characteristic impedance isAnswer: 10 Ω The terms RMS and average values apply only to sine waves.Answer: False