LMP2015 INTERSIL [Intersil Corporation], LMP2015 Datasheet - Page 11

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

INPUT CURRENTS
The LMP2015/LMP2016 input currents are different than
standard bipolar or CMOS input currents in that it appears as
a current flowing in one input and out the other. Under most
operating conditions, these currents are in the picoamp level
and will have little or no effect in most circuits. These currents
tend to increase slightly when the common-mode voltage is
near the minus supply. (See the typical curves.) At high tem-
peratures such as 85°C, the input currents become larger,
0.5 nA typical, and are both positive except when the V
near V
ages and high temperature, do not add resistance in series
with the inputs to balance the impedances. Doing this can
cause an increase in offset voltage. A small resistance such
as 1 kΩ can provide some protection against very large tran-
sients or overloads, and will not increase the offset signifi-
cantly.
FIGURE 2. The Output of a Chopper Stabilized Op Amp
FIGURE 3. The Output of the LMP2015/LMP2016
−
. If operation is expected at low common-mode volt-
(MAX432)
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CM
is
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PRECISION STRAIN GAUGE AMPLIFIER
This strain gauge amplifier (Figure 4) provides high gain
(1006 or ~60 dB) with very low offset and drift. Using the re-
sistors' tolerances as shown, the worst case CMRR will be
greater than 108 dB. The CMRR is directly related to the re-
sistor mismatch. The rejection of common-mode error, at the
output, is independent of the differential gain, which is set by
R3. The CMRR is further improved, if the resistor ratio match-
ing is improved, by specifying tighter-tolerance resistors, or
by trimming.
Extending Supply Voltages and Output Swing by Using a
Composite Amplifier Configuration
In cases where substantially higher output swing is required
with higher supply voltages, arrangements such as those
shown in Figure 5 and Figure 6 can be used. These configu-
rations utilize the excellent DC performance of the LMP2015
while allowing the superior voltage and frequency capabilities
of the LM6171 to set the dynamic performance of the overall
amplifier. For example, it is possible to achieve ±12V output
swing with 300 MHz of overall GBW (A
the worst case output shift due to V
LMP2015 output voltage is kept at about mid-point of its over-
all supply voltage, and its input common mode voltage range
allows the V
inverting operation) and tied to a small non-critical negative
bias in another (Figure 6, non-inverting operation). Higher
closed loop gains are also possible with a corresponding re-
duction in realizable bandwidth. Table 1 shows some other
closed loop gain possibilities along with the measured per-
formance in each case.
FIGURE 4. Precision Strain Gauge Amplifier
−
terminal to be grounded in one case (Figure 5,
OS
V
less than 4 mV. The
= 100) while keeping
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