Datasheet

LMP2014MT
www.ti.com SNOSAK6B –DECEMBER 2004–REVISED MARCH 2013
LMP2014 AS ADC INPUT AMPLIFIER
The LMP2014 is a great choice for an amplifier stage immediately before the input of an ADC (Analog-to-Digital
Converter), whether AC or DC coupled. See Figure 35 and Figure 36. This is because of the following important
characteristics:
a. Very low offset voltage and offset voltage drift over time 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.
b. Fast large-signal settling time to 0.01% of final value (1.4 μs) allows 12 bit accuracy at 100 KH
Z
or more
sampling rate.
c. No flicker (1/f) noise means unsurpassed data accuracy 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/√Hz
1/f corner frequency = 100 Hz
A
V
= 2000
Measurement time = 100 sec
Bandwidth = 2 Hz
This example will result in about 2.2 mV
PP
(1.9 LSB) of output noise contribution due to the op amp alone,
compared to about 594 μV
PP
(less than 0.5 LSB) when that op amp is replaced with the LMP2014 which has
no 1/f contribution. If the measurement time is increased from 100 seconds to 1 hour, the improvement
realized by using the LMP2014 would be a factor of about 4.8 times (2.86 mV
PP
compared to 596 μV when
LMP2014 is used) mainly because the LMP2014 accuracy is not compromised by increasing the observation
time.
d. Copper leadframe construction minimizes any thermocouple effects which would degrade low level/high gain
data conversion application accuracy (see discussion under " The Benefits of the LMP2014" section above).
e. Rail-to-Rail output swing maximizes the ADC dynamic range in 5-Volt single-supply converter applications.
Below are some typical block diagrams showing the LMP2014 used as an ADC amplifier.
Figure 36.
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