OA1ZHA Datasheet, PDF (23/35 Pages) STMicroelectronics – Fitness and healthcare

OA1ZHA, OA2ZHA, OA4ZHA
Application information
5.11
5.11.1
Application examples
Oxygen sensor
The electrochemical sensor creates a current proportional to the concentration of the gas
being measured. This current is converted into voltage thanks to R resistance. This voltage
is then amplified by OA1ZHA, OA2ZHA and OA4ZHA CMOS op amp (see Figure 47:
"Oxygen sensor principle schematic").
Figure 47: Oxygen sensor principle schematic
The output voltage is calculated using Equation 2:
Equation 2
V_{ou t} =
I × R – V_io ×
R_{2 + 1}
R₁
As the current delivered by the O2 sensor is extremely low, the impact of the Vio can
become significant with a traditional operational amplifier. The use of the chopper amplifier
of the OA1ZHA, OA2ZHA and OA4ZHA is perfect for this application.
In addition, using OA1ZHA, OA2ZHA and OA4ZHA op amp for the O2 sensor application
ensures that the measurement of O2 concentration is stable even at different temperature
thanks to a very good ∆Vio/∆T.
DocID025994 Rev 2
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