📡 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

The load impedance ZL of a CE amplifier has R and L in series. The phase difference between output and input will beAnswer: more than 180° but less than 270° If an amplifier with gain of - 1000 and feedback factor β = - 0.1 had a gain change of 20% due to temperature, the change in gain of the feedback amplifier would beAnswer: 0.2% In a BJT circuit a pnp transistor is replaced by npn transistor. To analyse the new circuitAnswer: replace all calculated voltages and currents by reverse values To protect the diodes in a rectifier and capacitor input filter circuit it is necessary to useAnswer: surge resistor In a CE amplifier the input impedance is equal to the ratio ofAnswer: ac base voltage to ac base current For a system to work, as oscillator the total phase shift of the loop gain must be equal toAnswer: 360° An amplifier has a large ac input signal. The clipping occurs on both the peaks. The output voltage will be nearly aAnswer: square wave The efficiency of a full wave rectifier using centre tapped transformer is twice that in full wave bridge rectifier.Answer: False .Assertion (A): CE amplifier is the most widely used BJT amplifier Reason (R): CE amplifier has zero phase difference between input and outputAnswer: A is correct R is wrong Assertion (A): For large signal variations an amplifier circuit has to be analysed graphically Reason (R): The output characteristics of a transistor is nonlinear.Answer: Both A and R are correct and R is correct explanation for A Negative feedback reduces noise originating at the amplifier input.Answer: False Maximum efficiency of class B power amplifier is 50%.Answer: False The self bias providesAnswer: stable Q point Consider the following statements : A clamper circuit 1. adds or subtracts a dc voltage to a waveform 2. does not change the waveform 3. amplifiers the waveform Which are correct?Answer: 1, 2 A forward voltage of 9 V is applied to a diode in series with a 1 kΩ load resistor. The voltage across load resistor is zero. It indicates thatAnswer: diode is open circuited Which power amplifier can deliver maximum load power?Answer: Class C A bridge rectifier circuit has input of 50 Hz frequency. The load resistance is RL and filter capacitance is C. For good output wave shape, the time constant RLC should be at least equal toAnswer: 100 ms In class C operation of an amplifier circuit, the collector current exists forAnswer: less than 180° of input wave An exponential amplifier has diode in feedback path.Answer: False DC amplifiers have a tendency to be unstable.Answer: True An amplifier with loop gain Aβ will be more stable for value of Aβ asAnswer: 0.7 The resolution of an n bit DAC with a maximum input of 5 V is 5 mV. The value of n isAnswer: 10 2's complement of binary number 0101 isAnswer: 1011 An OR gate has 4 inputs. One input is high and the other three are low. The outputAnswer: is high Decimal number 10 is equal to binary numberAnswer: 1010 Both OR and AND gates can have only two inputs.Answer: False A device which converts BCD to seven segment is calledAnswer: decoder In 2's complement representation the number 11100101 represents the decimal numberAnswer: -27 A decade counter skipsAnswer: binary states 1010 to 1111 BCD input 1000 is fed to a 7 segment display through a BCD to 7 segment decoder/driver. The segments which will lit up areAnswer: all