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Circuit #2 : Analog Input Amplifier
This circuit can be used to increase (or amplify) an input voltage while drawing negligible current from the input source (on the order of nanoamps!) As shown below, the circuit’s output is 16 times higher than the input, useful for converting low-voltage sensor outputs to use the full 0V to 5V range of an A/D converter.
The TLV2371 is a rail-to-rail op-amp (operational amplifier) that can output voltages over the full range of its supply voltage (0V to 5V) in this case. This means that the input signal can’t be larger than 5V/16, or 312.5mV. This circuit will not, for example, take 1V in and drive 16V out.
Other amplification factors (or gains) can be obtained simply by changing the values of R1 and R2. The amplification (gain) is set by:
Make sure that the sum of R1 and R2 isn’t too low else the op-amp won’t be able to supply the current that flows through those resistors. Try to keep  .
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