PX200 V2 Manual
10
Rev 1.1, Released, 15-01-2018
9
Noise
The output voltage noise contains a low frequency component (0.03 Hz to 20 Hz) that is independent of
the load capacitance; and a high frequency (20 Hz to 1 MHz) component that is approximately inversely
proportional to the load capacitance.
The noise is measured with an SR560 low-noise amplifier (Gain = 1000), oscilloscope, and Agilent 34461A
Voltmeter. The low-frequency noise is plotted in Figure 4. The RMS value is 120 uV with a peak-to-peak
voltage of 600 uV.
Figure 4. Low frequency noise from 0.03 Hz to 20 Hz
The high frequency noise (20 Hz to 1 MHz) is listed in the table below versus load capacitance. The total
RMS noise from 0.03 Hz to 1 MHz is found by summing the RMS values, that is
𝜎 = √𝜎
𝐿𝐹
2
+ 𝜎
𝐻𝐹
2
. For a load
capacitance of less than 1 uF, the noise is primarily broadband thermal noise; however, for a capacitance
of greater than 1 uF, the noise is primarily due to low-frequency noise.
Load Cap.
Bandwidth
HF Noise RMS
Total Noise RMS
10 nF
393 kHz
530 uV
543 uV
30 nF
431 kHz
586 uV
598 uV
100 nF
367 kHz
689 uV
699 uV
300 nF
208 kHz
452 uV
468 uV
1 uF
88 kHz
261 uV
287 uV
3 uF
30 kHz
106 uV
160 uV
10 uF
9.3 kHz
56 uV
132 uV
30 uF
3.7 kHz
52 uV
131 uV
100 uF
1.3 kHz
47 uV
129 uV
Table 5. RMS noise versus load capacitance (0.03 Hz to 1 MHz)
