Page 80 - Photodetection and Measurement - Maximizing Performance in Optical Systems

Fundamental Noise Basics and Calculations

Fundamental Noise Basics and Calculations 73

-30

-40

-50
9.5μA
Voltage (dBm) -60

-70
0.2μA

-80
0μA
-90

-100
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0
Frequency (MHz)
Figure 3.22 Frequency spectrum of the ZTX453 noise generator at current (bottom to top) of 0, 0.2,
1.1, 2.95, 9.5mA.

CD4006 CD4070 +5V
10nF
Vcc Vcc
Clock 4S
input 100k Clock output
4S 1S
(to input)
4S
1k
4S 1S
Gnd Gnd
6.8nF
Oscillator

Low-pass
filter
PRBS noise
output
Figure 3.23 A pseudorandom bit stream generator can be formed using a shift reg-
ister and a few gates for feedback.

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