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I'm designing a portable Ozone meter with an Arduino that read the data from the sensor and send it via LoRaWAN. I've found out this sensor that seems perfect for what I need.

My device runs at 3.3V and must have very limited current consumption. On the datasheet, I've read that the sensor consumption at 3V is 15uA which is perfect for me.

Now, as soon as the sensor has, besides the linear Vgas output, two other outputs (Vref and Vtemp) which, according to the datasheet, must be connected to a buffer before being read by the Arduino, I need a low power consumption buffer.

NOTE: High impedance output requires a buffer to connect to any measurement device.

At this point, I was in search of a low power consumption buffer that works at 3.3V and I find this which is a multiplexer buffer with two input (perfect for me) and an output (so I can use only an analog read if I set up correctly my Arduino FW). On the datasheet, it also says that I can switch off the buffer (using 0V as Vcc) and the current absorbed by the buffer is very low (0.5uA) which is again perfect.

Ioff is a feature that allows for powered-down conditions (VCC = 0 V). When VCC = 0 V, signals in the range from 0 V to 3.6 V can be applied to the inputs and outputs of the device. No damage occurs to the device under these conditions.

The only thing is that I can't find the current absorbed by the buffer while operating. Is it Icc=0.9uA?

As soon as I'm no expert in buffers, is there a better circuit/device to handle the sensor's outputs?

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That chip does not give an analog output, it is a digital multiplexer, your looking for an analog switch and a buffer, or 2 buffers,

I would suggest picking your favorite distributer and sorting by supply current, narrow it down to what you need, and then cross check the datasheets of the shortlists

E.g. here is a search link for any op amps under 1uA supply current, It may not remain valid as time goes on, but as it is a single column it should not be hard to reproduce.

Mouser Op Amp List

Equally if your only measuring that one voltage, you may make life easier for yourself by feeding the buffered VREF signal into the arduino VREF pin through a 5K resistor (with a 10-100nF capacitor to ground at the arduino vref pin) this way once external vref is selected you get results as a proportion of vref, with a lot less math.

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  • \$\begingroup\$ I've found the TSV99x which, I think, connecting the output with the - input should work as an analog buffer. I think it should be ok, isn't it? \$\endgroup\$ – NicoCaldo Aug 30 '19 at 12:26
  • \$\begingroup\$ low supply current, not bias current, TSV99x draws about 900uA idle, likely closer to 1.1mA as a buffer. \$\endgroup\$ – Reroute Aug 30 '19 at 12:31

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