RHF330 Datasheet, PDF (14/22 Pages) STMicroelectronics – Rad-hard 1 GHz low noise operational amplifier

Noise measurements
5
Noise measurements
The noise model is shown in Figure 30.
● eN: input voltage noise of the amplifier
● iNn: negative input current noise of the amplifier
● iNp: positive input current noise of the amplifier
Figure 30. Noise model
RHF330
+
R3
iN ⁺
_
N3
iN -
eN
Output
HP3577
Input noise:
8 nV/√Hz
R2
N2
R1
N1
The thermal noise of a resistance R is:
4kTRΔF
where ΔF is the specified bandwidth.
On a 1 Hz bandwidth the thermal noise is reduced to:
4kTR
AM00837
where k is the Boltzmann's constant, equal to 1,374.E(-23)J/°K. T is the temperature (°K).
The output noise eNo is calculated using the superposition theorem. However, eNo is not
the simple sum of all noise sources but rather the square root of the sum of the square of
each noise source, as shown in Equation 1.
Equation 1
eNo = V1² + V2² + V3² + V4² + V5² + V6²
14/22
Doc ID 15576 Rev 3