# EC GATE 2008 (Test 1)

Tag: ec gate 2008
Q.1
An 8085 executes the following instructions 2710 LXI H, 30A0 H 2713 DAD H 2414 PCHL All address and constants are in Hex. Let PC be the contents of the program counter and HL be the contents of the HL register pair just after executing PCHL. Which of the following statements is correct ?
A. PC = 2715H HL = 30A0H
B. PC = 30A0H HL = 2715H
C. PC = 6140H HL = 6140H
D. PC = 6140H HL = 2715H
Answer : Option C
Explaination / Solution:

2710H LXI H, 30A0H ; Load 16 bit data 30A0 in HL pair 2713H DAD H ; 6140H ⟶ HL 2714H PCHL ; Copy the contents 6140H of HL in PC Thus after execution above instruction contests of PC and HL are same and that is 6140H

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Q.2
For the circuit shown in the figure, D has a transition from 0 to 1 after CLK changes from 1 to 0. Assume gate delays to be negligible. Which of the following statements is true A. Q goes to 1 at the CLK transition and stays at 1
B. Q goes to 0 at the CLK transition and stays 0
C. Q goes to 1 at the CLK tradition and goes to 0 when D goes to 1
D. Q goes to 0 at the CLK transition and goes to 1 when D goes to 1
Answer : Option A
Explaination / Solution:
No Explaination.

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Q.3
The logic function implemented by the following circuit at the terminal OUT is A. P NOR Q
B. P NAND Q
C. P OR Q
D. P AND Q
Answer : Option D
Explaination / Solution:

From the figure shown below it may be easily seen upper MOSFET are shorted and connected to Vdd thus OUT is 1 only when the node S is 0, Since the lower MOSFETs are shorted to ground, node S is 0 only when input P and Q are 1. This is the function of AND gate.

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Q.4
In the following limiter circuit, an input voltage Vi = 10 sin100πt is applied. Assume that the diode drop is 0.7 V when it is forward biased. When it is forward biased. The zener breakdown voltage is 6.8 V
The maximum and minimum values of the output voltage respectively are A. 6.1V, - 0.7 V
B. 0.7 V, - 7.5 V
C. 7.5 V, - 0.7 V
D. 7.5 V, - 7.5 V
Answer : Option C
Explaination / Solution:
No Explaination.

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Q.5
Consider the following circuit using an ideal OPAMP. The I-V characteristic of the diode is described by the relation where VT = 25 mV, I0 = 1μ A and V is the voltage across the diode (taken as positive for forward bias). For an input voltage Vi = -1 V, the output voltage V0 is A. 0 V
B. 0.1 V
C. 0.7 V
D. 1.1 V
Answer : Option B
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Q.6
Consider the following assertions. S1 : For Zener effect to occur, a very abrupt junction is required. S2 : For quantum tunneling to occur, a very narrow energy barrier is required. Which of the following is correct ?
A. Only S2 is true
B. S1 and S2 are both true but S2 is not a reason for S1
C. S1 and S2 and are both true but S2 is not a reason for S1
D. Both S1 and S2 are false
Answer : Option A
Explaination / Solution:
No Explaination.

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Q.7
A memory less source emits n symbols each with a probability p. The entropy of the source as a function of n
A. increases as log n
B. decreases as log(1/n )
C. increases as n
D. increases as nlogn
Answer : Option A
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Q.8
At 20 GHz, the gain of a parabolic dish antenna of 1 meter and 70% efficiency is
A. 15 dB
B. 25 dB
C. 35 dB
D. 45 dB
Answer : Option D
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Q.9
The signal is
A. FM only
B. AM only
C. both AM and FM
D. neither AM nor FM
Answer : Option C
Explaination / Solution:
No Explaination.

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Q.10
A certain system has transfer function where α is a parameter. Consider the standard negative unity feedback configuration as shown below Which of the following statements is true?
A. The closed loop systems is never stable for any value of α.
B.  For some positive value of α, the closed loop system is stable, but not for all positive values.
C. For all positive values of α, the closed loop system is stable.
D. The closed loop system stable for all values of α, both positive and negative.
Answer : Option C
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