High-pass Filter

FC = 0.07 Hz

Low Noise

Preamplifier

G = 1000

2

nd Order

Low-pass Filter

FC = 10 Hz

G = 1

2

nd Order

Low-pass Filter

FC = 10 Hz

G = 10

2

nd Order

High-pass Filter

FC = 0.1 Hz

G = 10

Scope

VDD

REF_Z

REF_GND

HEATP

HEATM

+30 V

10 V

REF80

CL

Figure 8-6. 1/f Noise Test Setup

Typical 1/f noise (0.1Hz to 10Hz) distribution can be seen in Figure 8-7.

Noise (ppmp-p)

0

10

20

30

40

0.084

0.096

0.108

0.12

0.132

0.144

0.156

Figure 8-7. 0.1Hz to 10Hz Voltage Noise Distribution

The 1/f noise is in such a low frequency range that it is not practical to filter out which makes it a key parameter

for ultra-low noise measurements. Noise sensitive designs must use the lowest 1/f noise for the highest precision

measurements. Figure 8-8 shows the effect of 1/f noise over 10s.

REF80

SNAS856A – SEPTEMBER 2024 – REVISED MARCH 2025

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