General Description; Typical Application - National Semiconductor LM7705 Manual

Low Noise Negative Bias Generator

General Description

The LM7705 is a switched capacitor voltage inverter with a
low noise, −0.23V fixed negative voltage regulator. This de-
vice is designed to be used with low voltage amplifiers to
enable the amplifiers output to swing to zero volts. The −0.23
volts is used to supply the negative supply pin of an amplifier
while maintaining less then 5.5 volts across the amplifier. Rail-
to-Rail output amplifiers cannot output zero volts when oper-
ating 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 ADC's input, it can output a zero voltage sig-
nal and the full input range of an ADC can be used. The
LM7705 has a shutdown pin to minimize standby power con-
sumption

Typical Application

© 2009 National Semiconductor Corporation
LM7705
Features
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Applications
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201730
Regulated output voltage
Output voltage tolerance
Output voltage ripple
Max output current
Supply voltage
Conversion efficiency
Quiescent current
Shutdown current
Turn on time
Operating temperature range
8-Pin MSOP Package
True zero amplifier output
Portable instrumentation
Low voltage split power supplies
June 10, 2009
−0.232V
5%
4 mV
PP
26 mA
3V to 5.25V
up to 98%
78 µA
20 nA
500 µs
−40°C to 125°C
20173001
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