LMV1012-15 National Semiconductor Corporation, LMV1012-15 Datasheet - Page 13

• Manufacturer Part Number: LMV1012-15
• Description: LMV2011 - High Precision, Rail-to-rail Output Operational Amplifier, Package: Soic Narrow, Pin Nb=8
• Manufacturer: National Semiconductor Corporation

Application Information
LMV2011 AS ADC INPUT AMPLIFIER
The LMV2011 is a great choice for an amplifier stage imme-
diately before the input of an ADC (Analog-to-Digital Con-
verter), whether AC or DC coupled. See Figure 7 and Figure
8. This is because of the following important characteristics:
A) Very low offset voltage and offset voltage drift over time
B) Fast large-signal settling time to 0.01% of final value
C) No flicker (1/f) noise means unsurpassed data accuracy
and temperature allow a high closed-loop gain setting
without introducing any short-term or long-term errors.
For example, when set to a closed-loop gain of 100 as
the analog input amplifier for a 12-bit A/D converter, the
overall conversion error over full operation temperature
and 30 years life of the part (operating at 50˚C) would be
less than 5 LSBs.
(1.4µs) allows 12 bit accuracy at 100KH
pling rate.
over any measurement period of time, no matter how
long. Consider the following opamp performance, based
on a typical low-noise, high-performance commercially-
available device, for comparison:
Opamp flatband noise = 8nV/
(Continued)
Z
or more sam-
FIGURE 8.
13
D) Copper leadframe construction minimizes any thermo-
E) Rail-to-Rail output swing maximizes the ADC dynamic
1/f corner frequency = 100Hz
A
Measurement time = 100 sec
Bandwidth = 2Hz
This example will result in about 2.2 mV
output noise contribution due to the opamp alone, com-
pared to about 594µV
opamp is replaced with the LMV2011 which has no 1/f
contribution. If the measurement time is increased from
100 seconds to 1 hour, the improvement realized by
using the LMV2011 would be a factor of about 4.8 times
(2.86mV
mainly because the LMV2011 accuracy is not compro-
mised by increasing the observation time.
couple effects which would degrade low level/high gain
data conversion application accuracy (see discussion
under "The Benefits of the LMV2011" section above).
range in 5-Volt single-supply converter applications. Be-
low are some typical block diagrams showing the
LMV2011 used as an ADC amplifier (Figure 7 and Figure
8).
V
= 2000
PP
compared to 596µV when LMV2011 is used)
PP
(less than 0.5 LSB) when that
20051522
PP
(1.9 LSB) of
www.national.com