The LM7705 device is a switched capacitor voltage inverter with a low noise, −0.23 V
fixed negative voltage regulator. This device is designed to be used with low voltage amplifiers to
enable the amplifiers output to swing to zero volts. The −0.23 V is used to supply the negative
supply pin of an amplifier while maintaining less then 5.5 V across the amplifier. Rail-to-Rail
output amplifiers cannot output zero volts when operating from a single-supply voltage and can
result in error accumulation due to amplifier output saturation voltage being amplified by
following gain stages. A small negative supply voltage will prevent the amplifiers output from
saturating at zero volts and will help maintain an accurate zero through a signal processing chain.
Additionally, when an amplifier is used to drive an input of the ADC, the amplifier can output a
zero voltage signal and the full input range of an ADC can be used. The LM7705 device has a
shutdown pin to minimize standby power consumption.
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