Fundamentals of Electronics (ELGE-1A) — DU B. Sc. (Hons) Electronics Previous Year Question Papers

(c) A certain transistor has apc Of 0.98 and a collector leakage current Ico of IMA. Calculate the collector and base currents when Is = ImA. (a) What are the different biasing arrangements used with a transistor? Explain the working of a fixed bias circuit without RE (7) (b) Give the working of a voltage divider biasing circuit used with a NPN transistor. Also find the expressions of If and Vce for this circuit? (6) (c) Calculate the values of Ic and Vce for a voltage divider biasing circuit used with a NPN transistor. 7. (a) Draw the block representations of four types of negative feedback circuits. What is the difference between a negative and positive feedback? (7) (b) Derive an expression to illustrate that the voltage gain in an amplifier circuit with negative feedback is less than the gain without feedback. (6) (c) Calculate the gain A, of a negative feedback amplifier with gain A = 100 and feedback factor 1. (a) State and explain Kirchoff's Current Law with the help of an example. (3) (b) A voltage source of 10V is in series with a 2 S resistance between terminals A and B. Convert above combination to a current source in parallel with a resistance between terminals A and B. (3) (c) What do you mean by depletion region in a PN junction diode? (d) Explain why an ordinary junction transistor is called bipolar? (3) (e) Define the terms stability and stability factor for a transistor. _ (3) (f) What are the requirements of a transistor biasing circuit? (3) 2. (a) State superposition theorem and explain it with the help of an example. What is the limitation of this theorem? (7) respectively are in parallel with a current source of 9A. Using current divider rule, find current through all three resistors. (6) (c) A 2S resistance and a load resistance Ry are in series with a 6V voltage source. Which value of RL will absorb the maximum power from the voltage source? Also calculate the maximum power absorbed by Ry. (5) 3. (a). Draw the circuit diagram of a bridge rectifier. Explain its working with the help of necessary waveforms. Give its advantage over half wave rectifier. (7) (b) Draw the I-V characteristics of a Zener diode and explain its working in reverse bias. Define Zener breakdown voltage. (6) (o) Calculate voltage Vo and current I, in the following diode circuit: (5) 4. (a) Explain the working of a positive clamper circuit. Also draw its output waveform if a square wave is applied at the input. (7) (b) What is a negative clipper? Draw the circuit diagram of a negative clipper circuit and explain its working with the help of waveforms. (6) (c) Why LED is operated in forward bias and photodiode is operated in reverse bias? Give one application each of LED and photodiode. (5) 5. (a) Show the biasing arrangement for a PNP transistor in CB configuration so that it works in active region and explain its working. (7) (b) Sketch the typical input and output characteristics of a PNP transistor in CE configuration and explain its working. (6)