(A ) A = D (B) B = C (C) AD – BC = 1 (D) AD + BC = 1
2. For a short circuited transmission line, reflection coefficient is equal to
(A) zero (B) infinity (C) –1 (D) +1
3. An analog signal is band-limited to 4kHz, sampled at the Nyquist rate and the samples are quantized into 4 levels. The quantized levels are assumed to be independent and equally probable. If we transmit two quantized samples per second, the information rate is ________ bits / second.
(A)1 (B) 2 (C) 3 (D) 4
Explanation:: Since two samples are transmitted and each sample has 2 bits of information, then the information rate is 4 bits/sec.
4. The root locus plot for a system is given below. The open loop transfer function corresponding to this plot is given by
Answer:: (B)
Explanation:: ‘ x ‘ → indicates pole
‘ O’ → indicates zero The point on the root locus when the number of poles and zeroes on the real axis
to the right side of that point must be odd
5. A system is defined by its impulse response The system is
(A) stable and causal (B) causal but not stable (C) stable but not causal (D) unstable and non-causal
Explanation::
h(n) is existing for n>2 ; so that h(n)=0;n<0 ⇒ causal
6. A digital-to-analog converter with a full-scale output voltage of 3.5 V has a resolution close to 14m V. Its bit size is
A) 4 B) 8 C) 16 D) 32
7. The output Y in the circuit below is always ‘1’ when
(A) two or more of the inputs P,Q,R are ‘0’
(B) two or more of the inputs P,Q,R are ‘1’
(C) any odd number of the inputs P,Q,R is ‘0’
(D) any odd number of the inputs P,Q,R is ‘1’
Explanation:: The output Y expression in the Ckt is Y= PQ +PR+ RQ So that two or more inputs are ‘1’, Y is always ‘1’.
8. For the function f(x) = x2e-x , the maximum occurs when x is equal to
A) 2 B) 1 C) 0 D) -1 Correct
9. 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
Explanation :: Drift current, J E= σ
J= (nun + pup)qE So that it depends on carrier concentration and electric field.
10. A Zener diode, when used in voltage stabilization circuits, is biased in
(A) reverse bias region below the breakdown voltage
(B) reverse breakdown region
(C) forward bias region
(D) forward bias constant current mode
11. The modes in a rectangular waveguide are denoted by TEmn/TMmn where m and n are the eigen numbers along the larger and smaller dimensions of the waveguide respectively. Which one of the following statements is TRUE?
(A) The TM mode of the wave does not exist
(B) The TE10mode of the wave does not exist
(C) The TM10 and the TE10 modes both exist and have the same cut-off frequencies
(D) The TM10 and TM01 modes both exist and have the same cut-off frequencies
Explanation :: TM10 mode doesn’t exist in rectangular waveguide.
12. The Column-I lists the attributes and the Column-II lists the modulation systems. Match the attribute to the modulation system that best meets it
| Column-I | Column-II |
| P Power efficient transmission of signals | 1 Conventional AM |
| Q Most bandwidth efficient transmission of voice signals | 2 FM |
| R Simplest receiver structure | 3 VSB |
| S Bandwidth efficient transmission of signals with Significant dc component | 4 SSB-SC |
Explanation :: Power efficient transmission →FM
Most bandwidth efficient → SSB-SC Transmission of voice signal
Simplest receives structure → conventional AM Bandwidth efficient transmission of → VSB Signals with significant DC component
13. For the transfer function G(jw)= 5 +jω , the corresponding Nyquist plot for positive frequency has the form
Answer::- (A)
Explanation :: As we increases real part ‘5’ is fixed only imaginary part increases.
14. The trigonometric Fourier series of an even function does not have the
(A) dc term (B) cosine terms (C) sine terms (D) odd harmonic terms
Explanation :: f(t) is even function, hence bk=0 Where ‘ bk ‘ is the coefficient of sine terms
15. A silicon PN junction is forward biased with a constant current at room temperature. When the temperature is increased by 10ºC, the forward bias voltage across the PN junction
(A) increases by 60mV (B) decreases by 60mV (C) increases by 25mV (D) decreases by 25mV
Explanation :: For Si forward bias voltage change by -2.5mv/ deg C
For 100C increases, change will be 2.5*10= -25mV
16. The value of the integral
where c is the circle Z=1is given by(A) 0 (B) 1/10 (C) 4/5 (D) 1
17. Two D flip-flops are connected as a synchronous counter that goes through the following QBQA sequence 00–> 11–> 01–> 10–> 00 … The combination to the inputs DA & DB are
Answer :: D
18. A transmission line of characteristic impedance 50W is terminated in a load impedance ZL ,The VSWR of the line is measured as 5 and the first of the voltage maxima in the line is observed at a distance of λ/4 from the load. The value of ZL is
(A) 10Ω (B) 250 Ω (C) (19.23 +j46.15) Ω (D) (19.23-j46.15) Ω
19. When the output Y in the circuit below is ‘1’, it implies that data has
(A) changed from 0 to 1 (B) changed from 1 to 0 (C) changed in either direction (D) not changed
Exp: – When data is ‘0’, Q is ‘0’ And Q’ is ‘1’ first flip flop Data is changed to 1 Q is 1 → first ‘D’
Q’ is connected to 2nd flip flop, So that Q2=1 So that the inputs of AND gate is ‘1’==> y = ’1′
20. In amplifier application, FET is operated in
a) The controlled resistor region b) The controlled source region c) The aval anche breakdown region d) None
21. A helical antenna is used for satellite tracking because of its
a) broad bandwidth b) maneuverability c) circular polarization d) good front -to-back ratio
22. A1 A2 A3 are ideal ammeters. If A1 reads 5A, A2 reads 12A, then A3 should read
a) 7A b) 12A c) 13A d) 17A
23. The steady state current through 1H inductance
a) zero b) 5A c) 3A d) 6A
24. The total number of 128 8 RAM chips is needed to provide a memory capacity of 2048 bytes is:
a) 11 b) 16 c) 10 d) 8
25. PLL can be used to demodulate
a) DSB-SC signals b) PCM signals c) PAM signals d) FM signals
26. Compared to BJT, MOSFET enjoyi ng an advantage of
a) Able to handle hi gh power b) Ease of cont rol c) Requires less power in driving it d) None of these
27. Which of the following noise becomes important at microwave frequencies?
a) short noise b) transit time noise c) flicker noise d) thermal noise
28.
Answer :: D
29.
Answer :: A
30. DC-emphasis is used
a) to reduce overall modulation index
b) to attenuate l ow modul ation frequencies
c) to attenuate high modul ation frequencies
d) to attenuate mi d-band modulation frequencies.
31. A transmission li ne of 20 ohms characteristic impedance is connected to a load of 20+20j The normalized impedance is:
a) 400+400j b) 20j c) 40 +20j d) 1+1j
32.
Answer :: A.
Expalnation :: s(t) —> step response, Therefore impulse response is
33.The drain of an n-channel MOSFET is shorted to the gate so that VGS = VDS. The threshold voltage (VT) of MOSFET is 1 V. If the drain current (ID) is 1 mA for VGS = 2V, then for VGS = 3V, ID is
A) 2 mA B) 3 mA C) 9 mA D) 4 mA
34.The 8085 assembly language instruction that stores the content of H and L registers into the memory locations 2050H and 2051H, respectively, is
A) SPHL 2050 B) SPHL2051 C) SHLD 2050 D) STAX 2050
35. The cascade amplifier is a multistage configuration of
A) CC-CB B) CE-CB C) CB-CC D) CE-CC
36.Consider the following statements S1 and S2. S1: The b of a bipolar transistor reduces if the base width is increased. S2: The b of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct?
A) S1 is FALSE and S2 is TRUE B) Both S1 and S2 are TRUE C) Both S1 and S2 are FALSE D) S1 is TRUE and S2 is FALSE
37. Which interrupt has the highest priority?
A) INTR B) TRAP C) RST6.5 D) RST 5.5 – 7.5
38. BHE of 8086 microprocessor signal is used to interface the
A) Even bank memory B) Odd bank memory C) I/O D) DMA
39. What is the Address (SFR) for TCON, SCON, SBUF, PCON and PSW respectively?
A) 88H, 98H, 99H, 87H, 0D0H. B) 98H, 99H, 87H, 88H, 0D0H C) 0D0H, 87H, 88H, 99H, 98H D) 87H, 88H, 0D0H, 98H, 99H
40. In a PCM system, if the code word length is increased from 6 to 8 bits, the signal to quantization noise ratio improves by the factor
A) 8/6 B) 12 C) 16 D) 8
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