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AE_EC1405_EVENSEM_2011_MidSemesterSolutions

Module by: Bijay_Kumar Sharma. E-mail the author

Summary: This module gives the solutions of the questions asked in MisSemester Examination.

Solutions of Midesemester Examination_AE_EC1405_EVEN_2011

  1. i.Give the spectrum slot allocated for the following applications:
Table 1
Application Spectrum Slot
Medium Wave AIR local broadcast_AM 540kHz to 1.7Mhz
Short Wave Global Broadcast of different countries_AM 5.95MHz to 26.1MHz
Doordarshan TV Broadcast_ Channel 2 to 6 54MHz to 88MHz
AIR_FM broadcast 88MHz to 108MHz

ii. Nonlinear characteristics of the active device causes Amplitude Distortion or Harmonic Distortion. In RC-coupled Amplifier when input voltage exceeds 10mVpeak to peak the small signal approximation is vilated and Amplitude distortion occurs.

iii. When the full spectrum of the given intelligent signal say speech signal is not transmitted then Frequency Distortion occurs as Sqaure Wave passing through RC Low Pass Filter. If the Time Period(T) of the square wave is comparable to the time constant of RC Filter(τ) then rounding off of the edges occur. When T << τ, then the square wave is completely obliterated. Only the mean value or the DC part remains with slight ripple.

iv. Different Schemes of Biasing:

Table 2
Biasing Schemes Applications
Two Battery Biaing Expensive, cumbersome and preferred only for device characterrization
Fixed Biasing No feedback hence drift prone. Q-point drifts with temperature, aging and replacement.
Potential Divider Biasing No feedback hence drift prone. Q-point drifts with temperature, aging and replacement.
Self Biasing Through RE , negative current-series feedback is provided hence no drift of Q-point with temperatue, aging and replacement. Finds wide application in Discrete Amplifiers.
Collector-Base feedback bising Through RB, negative voltage shunt feedback is provided hence no drift of Q-point with temperature, aging and replacement. Finds wide application in Discrete Amplifiers.
Widlar Biasing This also has negative voltage shunt feedback hence no drift of Q-point with temperature, aging and replacement. Finds wide application in Integrated Circuit Amplifiers.

v. Frequency Domain Response of the magnitude of the Voltage Gain of Emitter Degenerate Amplifier:

Figure 1
Figure 1 (Picture 1.png)

The square wave response of the Emiter Degenerate Amplifier is the Time Domain Response. At 10kHz, rounding off of the edges of the square wave is taking place. At 100Hz, the top and bottom of the square wave are sagging or tilting.

vi. High Pass Filter behaves as differentiator at very low frequencies. It just produces positive spikes at positive edges and negative spikes at negative edges.

vii. Low Pass Filter behaves as integrator at very high frequencies. It gives the mean value of the input square wave .

viii. CRO display under Component Testing Mode for resistances:

Table 3
Resistance value Display
Very high resistance Inclined line with very low angle of inclination
Low resistance Inclined line with high angle of inclination
Open Circuit Horizontal line
Short Circuit Vertical line.
  1. Identify the Amplifier ? Emitter degenerate Amplifier.

Q point ICQ = 1mA and VCEQ = 5V

Parameters of h-model:

Table 4
h- parameter value
hie 2.6k+100ohm
hre 10-4
hfe 100
hoe 1/40k

Hybrid-π Parameters:

Table 5
Hybrid-π Parameters value
rx 100Ω
rπ 2.6kΩ
rµ 4M
ro 40k
βfo 100
Cπ 100pF
Cµ 5pF
Figure 2
Figure 2 (Picture 3.png)

  1. (a) Low Pass Filter R = 10k and C = 1µF

Therefore Time Constant = τ = RC = 10 msec ;

Upper Cut off Circular Frequency = ωh = (1/10)kradians/sec;

Upper Cut off Frequency = fh = 15.9Hz.

Bode Plot:

Figure 3
Figure 3 (Picture 4.png)

b. Time Domain Response of LPF:

Figure 4
Figure 4 (Picture 5.png)

  1. (a) This is a RC-coupled Amplifier.

(b) Q point ICQ = 1mA and VCEQ = 5V

Parameters of h-model:

Table 6
h- parameter value
hie 2.6k+100ohm
hre 10-4
hfe 100
hoe 1/40k

Hybrid-π Parameters:

Table 7
Hybrid-π Parameters value
rx 100Ω
rπ 2.6kΩ
rµ 4M
ro 40k
βfo 100
Cπ 100pF
Cµ 5pF

Figure 5
Figure 5 (Picture 6.png)

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