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THS6072 Datasheet, PDF (14/31 Pages) Texas Instruments – LOW-POWER ADSL DIFFERENTIAL RECEIVER | |||
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THS6072
LOW-POWER ADSL DIFFERENTIAL RECEIVER
SLOS290B â FEBRUARY 2000 â REVISED JUNE 2001
APPLICATION INFORMATION
noise calculations and noise figure (continued)
This brings up another noise measurement usually preferred in RF applications, the noise figure (NF). Noise
figure is a measure of noise degradation caused by the amplifier. The value of the source resistance must be
defined and is typically 50 ⦠in RF applications.
+ ȧȱ ȳȧ NF
10log
eni 2
2
È²Ç Ç È´ eRs
Because the dominant noise components are generally the source resistance and the internal amplifier noise
voltage, we can approximate the noise figure as:
ȧȧȧȧȱȲ È§È¡È¢Ç Ç Ç Ç È§È£È¤È³È´È§È§È§È§ + ) NF 10log 1
) ) 2
en
IN
4 kTRS
2
RS
Figure 41 shows the noise figure graph for the THS6072.
40.00
35.00
30.00
NOISE FIGURE
vs
SOURCE RESISTANCE
f = 10 kHz
TA = 25°C
25.00
20.00
15.00
10.00
5.00
0.00
10
100
1k
10k
Source Resistance â RS (â¦)
100k
Figure 41. Noise Figure vs Source Resistance
14
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