Conclusion

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Conclusion

Electrochemical sensors are widely used. They require specific op-amps to drive them and

to amplify the signal (current) they generate which is proportional to the concentration of

the gas being measured. The best choice of op-amp is generally a low-power, rail-to-rail

output, CMOS device. STMicroelectronics provides such devices. The most aggressive

device in terms of consumption is the TSU101 (600 nA typ at 3.3 V), but the TSV612 is

sufficient for several applications operating at 10 µA. If better accuracy is required, the

TSV711 (9 µA, 200 µV max) is a good choice. For the most demanding applications the

TSZ121 (29 µA @3.3 V, 5 µV max) should be considered. Table 2 illustrates the

advantages of the different op-amp products with regard to electrochemical sensors.

Table 2: Advantages of various op-amps

Product

Benefits (all specifications given at 3.3 V)

TSU101

TSU102

TSU104

Ultra low consumption: 600 nA typ

Battery life extension

TSV711

TSV712

TSV714

Good compromise between consumption and precision

Icc: 9 µA typ

Vio: 200 µV max

TSZ121

TSZ122

TSZ124

Excellent precision: Vio 5 µV max

Ideal for galvanic use

All op-amps in Table 2 are CMOS devices. They are available in small packages and

multiple-channel configurations for additional flexibility and space-saving.

If you plan to have a 4 mA to 20 mA output in your application, STMicroelectronics also has

high voltage op-amps that would meet your requirements.