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FACULTY OF SCIENCE – DEPARTMENT OF PHYSICS PH245 – ELECTRONICS THEORY -I TUTORIAL PROBLEMS 11 Give the output of the circuit shown in the diagram with respect to a sinusoidal input Vi = VP sin wt where VP = 15 V. Assume VZ of each zener to be 12 V. What is the output for VP = 10 V? 12 The circuit shown in the diagram is a clamped capacitor. Give the form of the output of the circuit with respect to a square wave input. If a load RL is connected across the output, show the form of the modified output. Assume T ~ CRL, where T is the period of the signal. 13 For the circuits shown in figure (a) and (b), find suitable values for RB. Assume hFE = 100, RC = 1 kW, VBE = 0.6 V and VC = VCC/2. What is the operating point for the two cases? Determine the new operating point for the two cases if hFE increases by 10% due to a temperate change. Comment on the result. 14 Consider the transistor switch circuit shown in diagram. The transistor has following characteristics: hFE = 100, ICO’ = 50 µA, VCE(sat) = 0.2 V. It is used to switch a bulb (load) on/off. (i) Calculate the maximum theoretical value possible for R1. (ii) What values would you choose for R1 and R? (iii) Determine IB, IC, VC and power dissipation in the transistor when the switch S is (a) open and (b) closed. (iv) What is the use of R and C? (v) If the light bulb in the circuit is replaced by a relay switch having same specifications, state the additional precautions that must be taken for the safe operation of the circuit. S C R1 R 10 V 0.1 A +10 V Vin C Vout ~ RL R Vi Vout RB RC + VCC = 10 V (a) RB RC + VCC = 10 V (b)
2 15 Consider the inverter circuit shown in the diagram. Assuming hFE = 100, determine (i) Vout for (a) Vin = 0 and (b) Vin = 5 V. (ii) The current through and the voltage across a load of 10 kW when the output is (a) HIGH and (b) LOW. (iii) The power dissipation in the transistor for the two cases (a) and (b) in (ii). (iv) Power dissipation in the load for the two cases. 16 (a) Show that the…