LMP2015 INTERSIL [Intersil Corporation], LMP2015 Datasheet - Page 12

• Manufacturer Part Number: LMP2015
• Description: High Precision, Rail-to-Rail Output Operational Amplifier
• Manufacturer: INTERSIL [Intersil Corporation]

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In terms of the measured output peak-to-peak noise, the fol-
lowing relationship holds between output noise voltage;
e
TABLE 1. Composite Amplifier Measured Performance
n
1000
100
100
500
AV
50
p-p, the closed-loop gain; A
FIGURE 5. Composite Amplifier Configuration
FIGURE 6. Composite Amplifier Configuration
200
100
200
100
R1
1k
Ω
100k
100k
100k
10k
10k
R2
Ω
0.67
1.75
2.2
C2
pF
10
8
V
, and −3 dB bandwidth; BW:
MHz
0.98
BW
3.3
2.5
3.1
1.4
(V/μs)
178
174
170
SR
96
64
(mV
en p-p
250
400
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37
70
70
PP
)
(1)
12
It should be kept in mind that in order to minimize the output
noise voltage for a given closed loop gain setting, one could
minimize the overall bandwidth. As can be seen from Equa-
tion 1, the output noise has a square root relationship to the
bandwidth.
In the case of the inverting configuration, it is also possible to
increase the input impedance of the overall amplifier by rais-
ing the value of R1. This can be done without having to
increase the feedback resistor, R2, to impractical values, by
utilizing a "Tee" network as feedback. See the LMC6442
datasheet (Application Information section) for more details
on this.
LMP2015 AS AN ADC DRIVER
The LMP2015 is a great choice for an amplifier stage imme-
diately before the input of an ADC (Analog-to-Digital Con-
verter) as an ADC driver, whether AC or DC coupled. See
Figure 7 and Figure 8. This is because of the following im-
portant 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 over-
all conversion error over full operation temperature and
30 year life of the part (operating at 50°C) would be less
than 5 LSBs.
(1.4 μs) allows 12-bit accuracy at a sampling rate of 100
kHz or more.
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:
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 LMP2015 which has no 1/f
contribution. If the measurement time is increased from
100 seconds to 1 hour, the improvement realized by using
the LMP2015 would be a factor of about 4.8 times
(2.86 mV
This is mainly because the LMP2015 accuracy is not
compromised by increasing the observation time.
Op amp flatband noise = 8 nV/
1/f corner frequency = 100 Hz
A
Measurement time = 100 sec
Bandwidth = 2 Hz
V
FIGURE 7. AC Coupled ADC Driver
= 2000
PP
compared to 596 μV when LMP2015 is used).
PP
(less than 0.5 LSB) when that
PP
(1.9 LSB) of
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