AN838 Datasheet, PDF (3/4 Pages) Silicon Laboratories – NANOPOWER CIRCUIT DESIGN IN LOW-FREQUENCY SENSOR APPLICATIONS

AN838
Figure 3. Op Amp and O2 Circuit Transfer Curve
2.2. Considerations and Results
With the components shown in Figure 1, the TS1001 op-amp specifications are:
Low supply current : ~1 µA
Low Input VOS: ~0.5 mV
Low Input IIN±: ~0.025 nA
High AVOL: ~90 dB
Rail-to-rail Inputs/Output (maximizes dynamic range and signal-to-noise ratio)
The circuit performance is:
Total circuit error: <3%
Total circuit power consumption: ~1µW
1.5 V AA battery lifetime: >285 years
O2 sensor replacement: >142 times before battery replacement
To minimize external gain error, ±1% tolerance resistor values are recommended. To reduce circuit bandwidth, an
external capacitor can be added across 10 M feedback resistor. For example, a 620 pF capacitor reduces the
circuit bandwidth to 25.6 Hz as shown in Figure 3.
3. Conclusion
An operational amplifier that combines precision dc specifications and low power consumption, such as the
TS1001 0.8V/0.6 µA op amp, produces an ultra low power signal conditioning circuit with low overall error for an
O2 sensor or other non-O2/low-frequency sensor applications. See the documentation for the TS1001 Op Amp.
For additional information, contact Silicon Labs.
Rev. 1.0
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