UM1737 Datasheet, PDF (10/14 Pages) STMicroelectronics – How to use the product evaluation board STEVAL-ISQ014V1

Theoretical and practical measurements
Equation 7
Vout
R^-R----g^-f-
R^-----s^-----×^------I ⁼ ₁^-----+-----_{1------A----+----V------R---}R_{---D---------g---}f_---
When:
Rf/Rg << AVD
Vout
R^-----s^-----×^------I ⁼
R^-R----g^-f-
1^-----+-----ε^--
≈
R^-R----g^{-f-(1 – ε )}
UM1737
Error(%)
=
1 + _R-^R----_g-^f-
–---_A----_V-----_D-----
×
100
Example:
Rf/Rg = 470
AVD = 120 dB (the minimum value for the TSZ121)
Error = –¹---_A--+--_V---^R--R--_D^------g--f-- × 100 = –0.047%
Clearly, the higher the gain of the schematics, the higher the inaccuracy, but in this
case the error is negligible.
10/14
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