Q. An optical pulse containing 6 × 106 photons is incident on a photodiode and 4.5 × 106 electron-hole pairs are created. The maximum possible quantum efficiency (in %) of the photodiode is Ans: 75 Sol: Number of incident photons ′N′=6×106 Number of electron-hole pairs generated n=4.5×106 Quantum efficiency of photo-diode

Q. An amplitude modulated signal is shown in the figure. The modulation index is (up to one decimal place) . Ans: 0.3

Q. A piezoelectric pressure sensor has a bandpass characteristic with cut-off frequencies of 0.1 Hz and 1 MHz, and a sensitivity of 100 mV/kPa. The sensor is subjected to a static constant pressure of 100 kPa. Its steady-state output will be (A) 0 V                       (B) 0.1 V                    (C) 1 V                       (D) 10 V Ans: 0.V  

Q. As shown in the figure, temperature q is measured using a K type thermocouple. It has a sensitivity of 40 mV/°C. The gain (G) of the ideal instrumentation amplifier is 25. If the output Vo is 96 mV, then the value of q (in °C) is _ . Ans: 95-97

Q. A 300 V, 5A, 0.2 pf low power factor wattmeter is used to measure the power consumed by a load. The wattmeter scale has 150 divisions and the pointer is on the 100th division. The power consumed by the load (in Watts) is . Ans: 200 Sol: Given that, voltage (V) = 300 V

Q. A voltage of 6 cos(100πt) V is fed as y-input to a CRO. The waveform seen on the screen of the CRO is shown in the figure. The Y and X axes settings for the CRO are respectively (A) 1 V/div and 1 ms/div                               (B) 1 V/div and 2 ms/div (C) 2 V/div and

Q. The number of comparators required for implementing an 8-bit flash analog-to-digital converter is (A) 8                           (B) 128                       (C) 255                      (D) 256 Ans: 255

Q. The representation of the decimal number (27.625)10 in base-2 number system is (A) 11011.110                                               (B) 11101.101 (C) 11011.101                                               (D) 10111.110 Ans: 11011.101

Q. For the 3-bit binary counter shown in the figure, the output increments at every positive transition in the clock (CLK). Assume ideal diodes and the starting state of the counter as 000. If output high is 1 V and output low is 0 V, the current I (in mA) flowing through the 50 Ω

Q. The diodes given in the circuit are ideal. At t = 60 ms, Vpq (in Volts) is____ Ans: 200