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AL-MC-Electronics / p.1 1. (89-I-40) 3. (91-I-43) An n-p-n transistor is used in the above circuit as a pulse shaper or a squarer. When a sinusoidal voltage A CRO is used to display the current transfer whose magnitude varies between +2 V and –2 V is characteristic curve of a transistor. How should applied to the input, what will be the output voltage? points P, Q and R be connected to the X-input, Y-input and the earth terminal of the CRO? X-input 2. Y-input Earth A. P Q R B. P R Q C. Q P R D. Q R P E. R P Q (90-I-39) 4. (92-I-30) The circuit above shows an NPN transistor and two resistors 10 k and 1 k connected to a 5 V d.c. supply. The current gain of the transistor is The graphs show the characteristics for a transistor 100. What is the value of the collector current? operating in the common emitter mode. IC is the collector current, IB is the base current and VCE is B. A 500 A C. 5 mA D. 50 mA A. 20 E. 500 mA B. 50 C. 80 D. 100 E. 150 A. 5 the potential difference between the collector and emitter. The current gain for this transistor is AL-MC-Electronics / p.2 5. (92-I-31) 7. (92-I-39) The graph shows the transfer characteristic of an electronic device. In the circuit shown above, D1 , D2 are two diodes used to rectify a sinusoidal a.c. supply. Each of the diodes has the I-V characteristic as shown. For a current to flow through R, the minimum The input is a sinusoidal voltage with a peak value value of A is of 1.5 V and a mean value of zero. Which one of the following waveforms best represents the A. 0.6 V variation of the output voltage with time? B. 1.2 V C. 0.3 D. (0.6) 2V E. (1.2) 2V 8. 2 V (93-I-32) Which of the following devices is/are used to store energy? 6. (92-I-32) In the circuit above, what is the voltage amplification? A. 50000 with inversion B. 1000 with inversion C. 50 with inversion D. 50 without inversion E. 50000 without inversion (1) an inductor (2) a capacitor (3) a photocell A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) AL-MC-Electronics / p.3 9. (93-I-40) Two electrical signals V1 and V2 are fed into an operational amplifier. The variations of V1 and V2 with time are shown above. Which of the following graphs represents the variation of the output Vout with time? The above diagrams show an NPN transistor circuit and its input/output voltage characteristic. What is the current amplification factor of the transistor? A. 10 11. (94-IIA-35) B. 30 Which of the following statements about an C. 60 operational amplifier is/are correct? D. 75 E. 150 (1) It amplifies the difference between the voltage at its two inputs. 10. (93-I-41) (2) For d.c., the open loop voltage gain is of the (3) order 10 . For a.c., the open loop voltage gain decreases 5 with increasing frequency. A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) AL-MC-Electronics / p.4 12. (94-IIA-36) 14. (95-IIA-29) A ‘black box’ containing two unknown components is connected to a cell, a resistor and an ammeter as shown The above figure shows an operational amplifier circuit which uses a 15 V supply (not shown). If the input potential is +0.5 V, what is the potential at point X? A current flows steadily no matter which way the box’s terminals are connected to the cell and the 13. A. –5 V same ammeter reading is obtained. The two B. –15 V components in the ‘black box’ could be C. +0.5 V D. +5 V A. two diodes in series. E. +15 V B. two diodes in parallel. C. two capacitors in parallel. D. a diode and a resistor in parallel. E. a diode and a capacitor in parallel. (94-IIA-39) 15. (95-IIA-43) An operational amplifier is connected as shown below with input voltage Vi 2 V In the above circuit, the waveform across the diode shown on the screen of the CRO should be What is the output voltage A. -6 V B. –4 V C. +4 V D. +6 V E. +12 V Vo ? AL-MC-Electronics / p.5 16. (96-IIA-30) 18. (96-IIA-32) Which of the following pairs of inputs would give a HIGH output from the above combination of NAND gates? Input A An input voltage ( Vin ) of 2.0 V is applied to an Input B ideal operational amplifier connected as shown. The (1) LOW HIGH (2) LOW LOW (3) HIGH HIGH current flowing through the 8 k resistor is A. 0.25 mA from X to Y. B. 0.80 mA from X to Y. A. (1) only C. 0.80 mA from Y to X. B. (3) only D. 1.0 mA from X to Y. C. (1) and (2) only E. 1.0 mA from Y to X. D. (2) and (3) only E. (1), (2) and (3) 19. (97-IIA-32) A circuit required for doubling the amplitude of a 17. (96-IIA-31) sinusoidal alternating voltage. Which of the following circuits might be suitable? In the above transistor circuit, the voltage across the A. (1) only base and the emitter is 0.5 V when the transistor B. (3) only works. The current amplification factor of the C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) transistor is 80. What input voltage ( Vin ) would give an output voltage ( Vout ) of 4 V? A. 0.25 V B. 0.50 V C. 0.75 V D. 1.00 V E. 1.25 V AL-MC-Electronics / p.6 20. (97-IIA-42) 22. (00-IIA-29) The figure shows a bridge rectifier circuit in which all the diodes are assumed ideal. The source is a In the above operational amplifier circuit, the output voltage 21. sinusoidal a.c. supply. Which of the following traces (I, II or III) would be displayed on a CRO Vout is connected across the load resistor R if A. -5 V B. –2.5 V (1) the diode D were reversed in the circuit, C. 0V (2) the diode D were removed leaving a break in D. +2.5 V E. +5 V the circuit? (98-IIA-40) In the above circuit, the output voltage from the operational amplifier is positive. Which of the following changes could cause the output voltage to change to negative? R1 (1) Increasing the value of (2) Decreasing the value of (3) Decreasing the light intensity on the LDR. A. (1) only B. (3) only C. (1) and (2) only D. (2) and (3) only E. (1), (2) and (3) R3 (1) (2) A. I II B. II II C. II III D. III II E. III III AL-MC-Electronics / p.7 23. (01-IIA-41) 25. (02-IIA-34) Which of the following is/are the advantage(s) of using negative feedback in an operational amplifier for voltage amplification? i. greater stability ii. larger voltage gain iii. no distortion of the output A. (1) only In the above transistor circuit, the voltage across B. (3) only the base and the emitter is 0.6 V when the C. (1) and (2) only transistor conducts. The current amplification D. (2) and (3) only factor of the transistor is 100. If the output voltage is 2 V, what is the value of R? 26. (02-IIA-43) The figure shows a typical voltage-amplifier circuit 24. A. 150 k built from a transistor with current gain 80. It B. 270 k operates normally on a quiescent collector current C. 300 k of 3 mA and with the base-emitter junction voltage D. 540 k E. 600 k (02-IIA-33) VBE 0.6 V . What should be the value of the base bias resistor RB? A. B. C. D. Which of the following combinations of a cell, an ideal diode and a resistor will give the above I-V relationship, where I and V are the applied current and voltage respectively? A. B. C. D. k 144 k 160 k 176 k 128 AL-MC-Electronics / p.8 27. (02-IIA-44) The figure shows an operational amplifier circuit. When V1 2.7 V and V0 0.9 V , what is the potential at P? A. 0V B. 0.6 V C. 2.1 V D. 2.4 V