ELECTRONICS AND COMMUNICATION ENGINEERING

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Pierce Dawson
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1 ELECTRONICS AND COMMUNICATION ENGINEERING Q1. A transmission line of characteristic impedance 50 Ω is terminated by a 50 Ω load. When excited by a sinusoidal voltage source at 10 GHz the phase difference between two points spaced 2 mm apart on the line is found to be 4π radians. The phase velocity of the wave along the line is (a) m/s (b) m/s (c) m/s (d) m/s Q2. A system is defined by its impulse response h(n) = 2 n u(n 2). The system is (a) stable and causal (b) causal but not stable (c) stable but not causal (d) unstable and non-causal Q3. Drift current in the semiconductors depends upon (a) only the electric field (b) only the carrier concentration gradient (c) both the electric field and the carrier concentration (d) both the electric field and the carrier concentration gradient Q4. An increase in the base recombination of a BJT will increase (a) the common emitter dc current gain β (b) the breakdown voltage bv ceo (c) the unity-gain cut-off frequency f t (d) the transconductance g m Q5. In a forward biased pn junction diode the sequence of events that best describes the mechanism of current flow is (a) injection and subsequent diffusion and recombination of minority carriers (b) injection and subsequent drift and generation of minority carriers (c) extraction and subsequent diffusion and generation of minority carriers (d) extraction and subsequent drift and recombination of minority carriers Q. A ( iˆ 2 ˆj ) of C (a) (b) 13 2ˆ i ˆj kˆ 13 iˆ ˆj kˆ B ( iˆ 3 ˆj 4kˆ) C ( 2ˆ i ˆj kˆ) Find the vector projection of A B in direction

2 (c) (d) 13 2ˆ i 2 ˆj kˆ 13 2ˆ i ˆj 2kˆ Q7. 2rˆ 3 ˆ 4kˆ convert into Cartesian at (230 o 4). (a) A x= (b) A x= (c) A x= A y= A z= A y= 1 2 A z= A y= A z= (d) A x= 3 2 A y= 1 2 A z=4 Q8. A 2iˆ 3 ˆj 4kˆ B ( 2ˆ r 3 ˆ 4kˆ) at point (224). Find the angle between these two vectors. (a) Sin 1 (b) Cos (c) Sin (d) Cos 2 29 Q9. f = 2rSinϕ find the projection of f in the direction xˆ at point (230 o 4) (a) Cos 3Sin

3 (b) Cos 3Sin (c) Sin 3Sin (d) Sin 3Cos Q10. A = Kr n where r 2 = x 2 +y 2 +z 2 (spherical). K= constant the value of n for which divergence of A is zero: (a) n = 2 (b) n = 1 (c) n = -2 (d) n = -1 Q11. If electric field established by three point charges Q 2Q and 3Q exerts a force 3F on 3Q and 2F on 2Q. What is the force exerted on Q. (a) F (b) -5F (c) -F (d) 5F Q12. Find power dissipation in the resistor for a given waveform: V m T/2 T (a) P av = P peak/2 (b) P av = P p/ 2 (c) P av = P p/ 3 (d) P av = P peak Q13. Find final value of the following function: F(s) = (a) 0 (b) 1 (c) (d) none ω s 2 +ω 2 Q14. The step response of the system is: C( = e 2t + 8e t (a) -7.5 (b) -7 (c) 7.5 (t > 0) The gain of the transfer function in time constant form will be:

4 (d) 7 Q15. For an AM each of the side band poweris given by 2kw and carrier power is given by 8kw. Find % of modulation. (a) 0% (b) 100% (c) 70% (d) 85% Q1. An unmodulated AM transmitter current is given by 5A. Find AM transmitter current with 50% of modulation. (a) 5.33A (b) 5.23A (c) 5.32A (d) 4.32A Q17. An AM transmitter current is given by 10A with carrier is modulated by single sinusoidal message signal with 40% of modulation with the carrier is simultaneously modulated by 2 nd message signal AM transmitter current is increased to 10.5A. Find % of modulation due to 2 nd message signal. (a) 55% (b) 47.5% (c) 50% (d) 47% Q18. An AM transmitter power is given by 500w. Find the amount of power saved if carrier and one of the carrier is suppressed with µ=0.8. (a) 349w (b) 394w (c) 439w (d) 493w Q19. A sinusoidal carrier of 1v 100MHz is product modulated by a sinusoidal message signal of 1v 1MHz. the resulting signal is passed through HPF of f cutoff=100mhz. filter output is added with sinusoidal signal of 1v 100MHz 90 o phase shift. Find the envelope of output. (a) Sin2π 10 t (b) 5 4 Cos2π 10 t (c) 5 4 Sin2π 10 t (d) Cos2π 10 t

5 Q20. AM and NBFM (Narrow Band FM) are having same modulation index were added. The resulting signal will be: (a) DSB (b) SSB (c) SSB with carrier (USB with carrier) (d) None Q21. If the drift velocity of holes under the field gradient of 100v/m is 5m/sec. what is the mobility? (a) 0.05 (b) 0.0 (c) 0.03 (d) 0.04 Q22. The minority carrier lifetime and diffusion constant in a semiconductor material are 100µs and 100cm 2 /s resp. Diffusion length of charge carriers: (a) 10 2 cm (b) 10-2 cm (c) 10 cm (d) 10-1 cm Q23. (37) 10 = ( )The decimal number is represented in (a) BCD code (b) Excess-3 code (c) Binary code (d) Gray code Q24. AND operation of (79H) and (- 5H) results in (a) 79H (b) 28H (c) 5H (d) 43H Q25. Which subtraction method is better for microprocessor (a) signed magnitude (b) 1's complement method (c) 2's complement method (d) floating point method Q2. The contents of memory location 4FFFH are The memory word could not be interpreted as: (a) Unsigned Binary number (b) Hexadecimal number (c) Octal number (d) Character

6 Q TB SRAM memory has (a) 43 address lines and 8 data lines (b) 42 address lines and 8 data lines (c) 41 address lines and 8 data lines (d) 40 address lines and 8 data lines Q number of 25 1 RAM IC are arranged in 1 rows and 8 columns to get memory of (a) 1kB (b) 2kB (c) 4kB (d) 8kB Q29. The smallest signed valid number can be stored in a memory location of 4kB RAM. (a) 0 (b) -128 (c) (d) -553 Q30. Which pin of 8085 microprocessor is tri-stated and output? (a) SOD (b) HOLD (c) INTA (d) RD Q31. Which pin of 8085 microprocessor is input pin? (a) READY (b) HLDA (c) ALE (d) SOD Q32. How many instructions are in the instruction set of 8085 microprocessor? (a) 250 (b) 240 (c) 25 (d) 24 Q33. If the status of the control lines S1 and SO is LOW then microprocessor is performing: (a) Reset operation (b) HOLD operation (c) Halt operation (d) Interrupt acknowledge

7 Q34. Upon reset of microprocessor the contents of accumulator Program counter and stack pointer becomes (a) 00H 0000H and 0000H respectively (b) 00H FFFFH 0000H (c) 00H 0000H FFFFH (d) none of above Q35. In the Processor Status Word (PSW) of microprocessor the accumulator carry flag and auxiliary carry flag are cleared after the execution of: (a) ANA A instruction (b) XRA A instruction (c) ADD A instruction (d) SUB A instruction Q3. When SUB A instruction is executed what will the status of carry zero and auxiliary carry flags in the Processor Status Word (PSW) of microprocessor (a) 0 0 and 0 respectively (b) 0 1 and 0 respectively (c) 0 1 and 1 respectively (d) 1 1 and 1 respectively Q37. How many data transfer instructions are in the instruction set of 8085 microprocessor? (a) 84 (b) 74 (c) 4 (d) 54 Q38. Upon going HIGH for a time the RST 5.5 input will cause the 8085 microprocessor to save the program counter contents in the stack and jump to memory location. (a) 0020H (b) 0024H (c) 0028H (d) 002CH Q39. The contents of program counter when the microprocessor is reading 2FFFH memory location will be: (a) 2FFEH (b) 2FFFH (c) 3000H (d) none of above Q40. In 8085 microprocessor during POP operation stack pointer is (a) incremented by one (b) incremented by two

8 (c) (d) decremented by one decremented by two Q41. Carry flag is not affected after the execution of (a) ADD B (b) SBB B (c) INR B (d) ORA B Q42. Register indirect addressing is followed by (a) PCHL (b) XCHG (c) DAA (d) RET Q43. Which of following is incorrect? (a) 11100B 10001B = 01011B (b) 15EH = 350 (c) 37.4O = B (d) (81) 10 = ( ) 2 Q44. The race around exist in J-K flip-flop if (a) J = 0; K = 1 (b) J = 1; K = 0 (c) J = 0; K = 0 (d) J = 1; K = 1 Q45. Which is dual of A + (B + (AC)) + D (a) A + (B (A + C) ) + D (b) A ( B + AC) D (c) A + (B (A + B) ) D (d) A ( B ( A + C ) ) D Q4. The following functions are to be implemented using a decoder F 1 m( ) F 2 m( ) The minimum configuration of decoder is (a) 2- to - 4 line (b) 3- to - 8 line (c) 4- to - 1 line (d) 5- to - 32 line Q47. Complemented output of clocked D flip flop is given to input of the flip flop. What will be the frequency of output? (a) Twice the input clock frequency

9 (b) (c) (d) Same as the input clock frequency Half the input clock frequency Inverse of input clock frequency Q number of 25 1 bit RAM IC are arranged in 4 rows and 8 columns to get memory of (a) 1kB (b) 2kB (c) 4kB (d) 8kB Q49. The smallest signed valid number can be stored in a memory location of 1kB RAM. (a) 0 (b) -128 (c) (d) -553 Q50. Initial state of MOD-1 down counter is After 37 clock pulses the state of counter will be (a) 1011 (b) 0110 (c) 0101 (d) 0001 Q51. A 8-bit D/A converter has a full scale output voltage of 20 V. The output voltage when the input is (a) 10 mv (b) 78 mv (c) 20 V (d) 17 V Q52. The characteristic equation of T- flip flop is (a) Q( t 1) TQ( TQ( (b) Q( t 1) TQ( TQ( (c) Q( t 1) TQ( (d) Q( t 1) TQ( TQ( Q53. The minimum number of NAND gates required to implement the Boolean function A AB ABC (a) Zero (b) 01 (c) 04 (d) 07

10 Q54. The number of unused states in a 4-bit Johnson counter is (a) 2 (b) 4 (c) 8 (d) 12 Q55. ( X Y )( X Z)( Y Z) (a) ( X Y )( Y Z) (b) ( X Z)( Y Z) (c) ( X Y)( X Z) (d) ( X Y)( X Z) Q5. If (2.3) 4 + (1.2) 4 = (y) 4. What is the value of y? (a) 10.1 (b) (c) 10.2 (d) 1.02 Q57. Given (135) X +(144) X = (323) X. What is the value of base? (a) 3 (b) 5 (c) (d) 12 Q58. A decade counter is applied with frequency of 10MHz then output frequency is (a) 3Hz (b) 1 MHz (c) 20 KHz (d) 10 MHz Q59. Convert (25.25) 10 into binary. (a) ( ) 2 (b) ( ) 2 (c) (11.101) 2 (d) ( ) 2 Q0. Convert (254) 1 into ( ) 1 (a) (FE) 1 (b) (EE) 1 (c) (AC) 1 (d) (BAD) 1

11 Q1. Simplify AB ABC ABCD (a) (b) (c) (d) A AC AB AB AB AC AC AC Q2. ExOR and AND gate required for 2 1 MUX (a) ExOR=1 AND=1 (b) ExOR=2 AND=2 (c) ExOR=2 AND=1 (d) ExOR=1 AND=2

Electronics Eingineering

Electronics Eingineering 1. The output of a two-input gate is 0 if and only if its inputs are unequal. It is true for (A) XOR gate (B) NAND gate (C) NOR gate (D) XNOR gate 2. In K-map simplification, a