herunterladen
LM7705
+
-
C
RES
C
FLY
C
OUT
+ In
- In
SHUTDOWN
low voltage
amplifier
true zero
output voltage
-V
+V
+V
-0.23V
C
F+
V
SS
SD
V
DD
V
SS
V
OUT
C
RES
C
F-
User's Guide
SNVA359B–October 2008–Revised May 2013
AN-1883 LM7705 Evaluation Board
1 General Description
This evaluation board is designed to demonstrate the functionality of Texas Instruments LM7705 Low
Noise Negative Bias Generator. The board has a dual Operational Amplifier that can be connected to
ground or biased with the on board LM7705. In the last case a True zero amplifier is demonstrated.
2 Basic Operation
The LM7705 is a switched capacitor voltage inverter with a low noise, −0.23V 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, having a single supply. The -0.23 Volts is used to supply the negative supply pin of an
amplifier. Rail-to-rail output amplifiers cannot output zero voltage 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. This is illustrated in
Figure 1.
Additionally when an amplifier is used to drive an ADC's input, it can output a zero voltage signal and the
full input range of an ADC can be used. The LM7705 has a shutdown pin to minimize standby power
consumption.
Figure 1. Typical LM7705 Application
All trademarks are the property of their respective owners.
1
SNVA359B–October 2008–Revised May 2013 AN-1883 LM7705 Evaluation Board
Submit Documentation Feedback
Copyright © 2008–2013, Texas Instruments Incorporated
Verzeichnis
- ・ Blockdiagramm on Seite 2
- ・ Beschreibung der Funktionen on Seite 1
- ・ Anwendungsbereich on Seite 7
