COMMUNICATION SYSTEM EECB353
CHAPTER 7- PART 2
NOISE ANALYSIS
Dr Norazizah Mohd Aripin
Department of Electronics & Communication Engineering
Universiti Tenaga Nasional

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Gain and Attenuation
■
Most circuits in are used to manipulate signals to
produce a desired relectronic communication esult.
■
All signal processing circuits involve:
–
Gain
–
Attenuation

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Gain and Attenuation
■
Gain means amplification. It is the ratio of a circuit’s
output to its input
.
■
The number obtained by dividing the output by the input
shows how much larger the output is than the input.
■
A positive (+) dB value indicates that the output power is
greater than the input power which indicates power gain.
A
V
=
=
output
input
V
out
V
in

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■
Most amplifiers are also power amplifiers, so the
same procedure can be used to calculate power gain
A
P
where
P
in
is the power input and
P
out
is the power
output.
Power gain (
A
p
) =
P
out
/
P
in
■
An amplifier is
cascaded
when two or more stages are
connected together.
■
The overall gain is the product of the individual
circuit gains
.
Gain and Attenuation
A
1
A
2
A
3
A
T
= A
1
x A
2
x A
3

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Example 1:a)The power output of an amplifier is 6 watts (W). The power gain is 80. What is the input power?b) Three cascaded amplifiers have power gains of 5, 2, and 17. The input power is 40 mW. What is the output power?Gain and Attenuation

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