1 R F R C V CC v i 5V 5V Detailed solution of IES 2103 (ECE) objective Paper – II: Set – ‘A’ 1. (C) Here output impedance is fe F 0 C 0 h R R R || r gm 1 1 A Here fe 0 C C h A gm R .R r So 0 50 A 4K 200 1k So F 0 C R 40K R R || 4K || 1 1 1 1 200 200 0 R 4K 2. (D) But it should be 2.84 mA CEO CBO I 1I 410 1 .5 81 Now C B CBO I I 1I 81 30 410 2430 410 C I 2840 A 2.84 mA 3. (C) In general R. bias current of a diode depends upon temperature only but for Si due to recombination it depends upon R. bias voltage also. so in general it is indep of R. bias but depends in case of Si. 4. (D) Let Transistor is in saturation region then using (B–E) Loop. B B 4.2 5 100 I 0.8 I mA 100 C C 4.8 5 5I 0.2 I mA 5 For saturation condition is C B I I but here is not given so one can’t decide whether it is in saturation or active region.
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II: Set ‘A’ VCC R v - Panacea Institute · Detailed solution of IES 2103 (ECE) objective Paper – II: Set – ‘A’ ... For series LCR 0 0 L 1 ... It is an astable multivibrator
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1
RF RC
VCC
vi
5V
5V
Detailed solution of IES 2103 (ECE) objective Paper – II: Set – ‘A’
1. (C)
Here output impedance is
feF0 C
0
hRR R || r
gm11A
Here fe0 C C
hA gm R .R
r
So 0
50A 4K 200
1k
So
F
0 C
R 40KR R || 4K ||
11 11 200200
0R 4K
2. (D) But it should be 2.84 mA
CEO CBOI 1 I 410 1 .5 81
Now C B CBOI I 1 I 81 30 410 2430 410 CI 2840 A 2.84 mA
3. (C) In general R. bias current of a diode depends upon temperature only but for Si due to
recombination it depends upon R. bias voltage also.
so in general it is indep of R. bias but depends in case of Si.
4. (D)
Let Transistor is in saturation region then using (B–E) Loop.
B B
4.25 100I 0.8 I mA
100
C C
4.85 5I 0.2 I mA
5
For saturation condition is CB
II
but here is not given so one can’t decide whether it is
in saturation or active region.
2
C
Q2 Q1
RRC2RC1
VCC
Trigger
RC
Cc
vo
Cz
Cb
vi
R2
R1
Re
VCC
FrequencyfL
Gain
5. (C)
It has one stable state and one quasi stable state. Other names are one shot, single step circuit,
gate circuit & delay circuit it is called a delay circuit because Monostable generates a fast
transition at predetermined time T after i/p trigger. It is called delay circuit it generates
rectangular waveform which can be used to gate other circuit so it is called gate circuit.
Main applications are gate and delay circuit. Since gating circuits generate rectangular wave
which can be used in counters. It is used for changing pulse width but does not mean in
regeneration of distorted output.
6. (D) 1
* nH Hf f 2 1 *
H Hn 2, f 0.64 f
7. (D)
Low frequency response depends upon coupling, by pass and blocking capacitor.
Value of Lf is inversely proportional to capacitance, so it can be improved or increased by
reducing any one of capacitors.
8. (C) 0fQ
B.W
For increasing band width Q factor must be decreased. So option (1) is not correct.
9. (C) if iZ Z 1 A 1K 1 0.99 100 100Kohm
0of
Z 100Z 1
1 A 1 0.99 100
3
R
C
–
+
vo
vi
C2
Q2 Q1
R2RC2
RC1
VCC
C1
R1
10. (A) Here ii/p v is given as
3
iv 5sin 2 10 t mV
Now
t
0 i
0
1v v dt
RC
t
t 03 3 3
0 5 6 3
0
1 10 5 1v 5sin 2 10 t cos 2 10 t cos 2 10 t 1
10 10 2 10 40
11. (C) Here Q is not 105 but 105
For series LCR 0
0
L 1Q &Q
R RC
5
12
5
150
10 400 C
1C 500 10 F
10 400 50
12. (B) with negative feedback
f
A 100A
1 A 1 0.03 100
f
100A 25
4
13. (B) It has resistive negative feedback so system will be stable at all frequency.
14. (C) For HWR 1.21& FWR 0.48
15. (A) In general differential amplifier is used at i/p stage to () high i/p impedance and this has
high CMRR also
16 . (B) HWR 40.6% & FWR 81.2%
17. (A) CMRR in dB 20log CMRR
1080dB 20log CMRR
So 4 d
c
ACMRR 10
A
4
c 4
2 10A 2
10
18. (C) ECL has the highest speed because it is nonsaturated logic and does not enter into Saturation
so time taken in removal of storage delay time is reduced or becomes zero.
19. (C) It is time taken in reacting from 10% to 90%
20. (A)
It is an astable multivibrator
4
01001000 0111
(8 7 4)10
00 01 11 10
0
1
BCA
1 1
1
H.S.B
H.S.B
x
y
D
Z D
D
1 1 2 2
3 8 4 8 5 4 8
5 3
5
5
T 0.69R C 0.69R C
T 0.69 2 10 10 0.69 2 10 5 10 0.69 2 10 2 10 5 10
T 0.69 2 10 10
1 1 10f 1420.85 Hz
T 0.69 102 10 102 0.69
21. (B) Transistor becomes heated when it enters into saturation or is in saturation or come back from
saturation to cut-off
D CE C D CP V .I P due to in I .
So power dissipation at collector () and which dissipates same heat.
22. (A)
23. (A) f A B A B AA AB BA B B A A B
24. (B) f ABD ABD AB D D = AB
25. (C) f A AB ABC
f A AB ABC A AB (A A)(A B) (A B)
For (A B) 4 NAND gates are required.
26. (A) f A,B,C,D A BC B CD AB ACD BC BCD
27. (None)
f A B A B B B A A
f AB AB BA
28. (A)
f AB BC
29. (B) FET has more temperature stability, high i/p impedance and less noisy than BJT.
30. (B) f AB ACD
f AB C C D D ACD B B
AB CD CD CD CD ABCD ABCD
ABCD ABCD ABCD ABCD ABCD ABCD
ABCD ABCD ABCD ABCD ABCD
31. (B) Full subtractor 2H.S 1 OR gate
5
32. (C) MUX is a Many to one switch and in which all parallel i/ps can be changed to serial
output.MUX is not used for chip select but decoder is used for chip select.
33. (C) & (D) are correct.
PROM Fixed AND + Programmable OR
PLA Programmable AND & OR
PAL Fixed OR + Programmable AND
34. (A)
n 1
n
n
J K Q
0 0 Q
0 1 0
1 0 1
1 1 Q
Here nQ 0 and n 1Q 1
it means J 1 & K X
35. (B) Output depends upon past output as well as present inputs.
36. (B) Dual slope ADC has the highest accuracy on cost of its speed.
37. (None)
2
s 1G s
s s 1
For D.C. gain put s = 0
Ps 0
G 0 1
K limG s 1
So ss
1e 0.5
1 1
38. (D)
2
2
d x t dx t5 7x t y t
dt dt
2s 5s 7 X s Y s
Characteristic equation is 2s 5s 7 0
2
n n
n
7 & 2 5
2.57 & 0.94
7
39. (B)
2
d1 d
1
C s s 4s 1 1
K .sR s 4s s 1 K1
s 4s 1
2
d
2
d
100 1
C s 4s s 1 K
100R s1
4s s 1 K
6
2
d
C s 100
R s 4s s 1 K 100
Characteristic equation is 2
d4s s 1 K 100 0
2
d
ss 1 K 25 0
4
d
n n
1 K5 2
4
d d40 0.5 1 K K 19
40. (C) Settling time s
n
4t
Here n 10 & n2 10
So s
4t 0.8sec
5
41. (D) 4 3 2s 20Ks 5s 10s 15 0
4
3
2
1
0
s 1 5 15
s 20K 10 0
100K 10s 15 0
20K
300K 20Ks 10 0 0
100K 10
s 15
For stable system check
300K 2K10
10K 1
2100K 10 600K
10K 1
2
2
100K 10 600K
600K 100K 10 0
100 10000 24000
K2 600
This equation will be always +ve, so it will be unstable for all values of K.
42. (C) 3 2s 4s s 6 K 0
3
2
1
0
s 1 1
s 4 K 6
4 K 6s 0
4
s K 6
For stable operation 10 K 0
K 10
7
K 6 0 K 6
43. (A)
44. (C) 2
K1 0
s s 6s 10
3 2s 6s 10s K 0
3
2
1
0
s 1 10
s 6 K
Ks 10 0
6
s K
For oscillations K
10 06
K 60
For frequency 26s K 0
26 K 0 10 3.16 Rad/ sec
45. (D)
C s G s
R s 1 G s H s
For closed loop poles
1 G s H s 0
2
2
11 0 s 4 4s 1 0
s 2
2 4 16 20 4 2js 5 4s 0 s s 2 1j
2 2
46. (A) Band width is Noise filtering characteristics higher is the B.W, higher is noise value.
47. (D) 21
pM e
48. (B) Since K = 10
So gain in dB at 1 will be 20 dB.
49. (C)
50. (C)
51. (C) G.M 20log40 20log20
20 log 2 6dB
G.M is value of additional gain to make a system unstable.
52. (D) For 0 system is undamped so marginally stable hence P.M = 0
So here option (4) is correct and option (3) is incorrect. Hence (D) is correct.
Alternatively formula for P.M. in terms of is:
8
1
2 4
2P.M. tan
2 1 4
53. (D)
1G s H s
s s 1
190º tan
For PCF 180º 1tan 90º tan90º
2
1G s H s 0
1
1G.M
G s H s
54. (A) Addition of zero means system becomes phase lead system.