Filtering

AN4348

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DocID025166 Rev 1

Note that the output noise between 0.1 Hz and 10 Hz is not simply:

This is because of the sensor model and the GBP limitation of the op-amp.

The integrated noise of the op-amp over the bandwidth 0.1 Hz to 10 Hz gives us the first

impression of the noise caused by the op-amp in the application:

In the case of a very low signal (large gain, few ppm of gas), an op-amp with low noise is

required. For such an application, the TSZ121 is a perfect choice. It has a very low noise at

low frequency (1.4 µVpp only on the 0.1 Hz to 10 Hz bandwidth). In addition, 1/f noise is

reduced due to the internal architecture (chopper) of this op-amp.