LMP2012MMX National Semiconductor, LMP2012MMX Datasheet - Page 13

• Manufacturer Part Number: LMP2012MMX
• Description: IC,Operational Amplifier,DUAL,TSSOP,8PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LMP2012MMX

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Application Information
LMP201X AS ADC INPUT AMPLIFIER
The LMP201X 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 (1.4
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.
µs) allows 12 bit accuracy at 100 KH
rate.
over any measurement period of time, no matter how
long. Consider the following op amp performance, based
on a typical low-noise, high-performance commercially-
available device, for comparison:
Op amp flatband noise = 8nV/
Z
(Continued)
or more sampling
FIGURE 8.
13
D) Copper leadframe construction minimizes any thermo-
E) Rail-to-Rail output swing maximizes the ADC dynamic
1/f corner frequency = 100 Hz
A
Measurement time = 100 sec
Bandwidth = 2 Hz
This example will result in about 2.2 mV
output noise contribution due to the op amp alone, com-
pared to about 594 µV
op amp is replaced with the LMP201X which has no 1/f
contribution. If the measurement time is increased from
100 seconds to 1 hour, the improvement realized by
using the LMP201X would be a factor of about 4.8 times
(2.86 mV
used) mainly because the LMP201X accuracy is not
compromised 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 LMP201X" section above).
range in 5-Volt single-supply converter applications. Be-
low are some typical block diagrams showing the
LMP201X used as an ADC amplifier (Figure 7 and Figure
8).
V
= 2000
PP
compared to 596 µV when LMP201X is
PP
(less than 0.5 LSB) when that
20071522
PP
(1.9 LSB) of
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