TS616 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'TS616' PDF : 36 Pages View PDF
Noise measurements
TS616
The output noise eNo is calculated using the Superposition Theorem. However eNo is not
the 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
No = V12 + V22 + V32 + V42 + V52 + V62
Equation 2
No2 = eN2 × g2 + iNn2 × R22 + iNp2 × R32 × g2
…+
⎛
⎝
RR-----21--⎠⎞
2
×
4kTR1
+
4kTR2
+
⎝⎛ 1
+
RR-----21--⎠⎞ 2
×
4kTR3
The input noise of the instrumentation must be extracted from the measured noise value.
The real output noise value of the driver is:
Equation 3
eNo = (Measured)2 – (instrumentation)2
The input noise is called the Equivalent Input Noise as it is not directly measured but is
evaluated from the measurement of the output divided by the closed loop gain (eNo/g).
After simplification of the fourth and the fifth term of Equation 2 we obtain:
Equation 4
=
eN2 ×
g2 + iNn2 ×
R22 + iNp2 ×
R32 ×
g2…+ g ×
4kT
R
2
+
⎛
⎝
1
+
RR-----21--⎠⎞
2
×
4kT
7.1
Measurement of eN
If we assume a short-circuit on the non-inverting input (R3=0), Equation 4 becomes:
Equation 5
No = eN2 × g2 + iNn2 × R22 + g × 4kTR2
In order to easily extract the value of eN, the resistance R2 will be chosen as low as
possible. On the other hand, the gain must be large enough:
● R1=10 Ω, R2=910 Ω, R3=0, Gain=92
● Equivalent input noise: 2.57 nV/√Hz
● Input voltage noise: eN=2.5 nV/√Hz
24/37
Share Link: 
