LMV862MMEVAL National Semiconductor, LMV862MMEVAL Datasheet - Page 13

• Manufacturer Part Number: LMV862MMEVAL
• Manufacturer: National Semiconductor

Specifications of LMV862MMEVAL

• Lead Free Status / Rohs Status: Supplier Unconfirmed

Application Information
INTRODUCTION
The LMV861 and LMV862 are operational amplifiers with ex-
cellent specifications, such as low offset, low noise and a rail-
to-rail output. These specifications make the LMV861 and
LMV862 great choices for medical and instrumentation appli-
cations such as diagnosis equipment and power line moni-
tors. The low supply current is perfect for battery powered
equipment. The small packages, SC70 package for the
LMV861, and the MSOP package for the dual LMV862, make
these parts a perfect choice for portable electronics. Addi-
tionally, the EMI hardening makes the LMV861 and LMV862
a must for almost all op amp applications. Most applications
are exposed to Radio Frequency (RF) signals such as the
signals transmitted by mobile phones or wireless computer
peripherals. The LMV861 and LMV862 will effectively reduce
disturbances caused by RF signals to a level that will be hard-
ly noticeable. This again reduces the need for additional
filtering and shielding. Using this EMI resistant series of op
amps will thus reduce the number of components and space
needed for applications that are affected by EMI, and will help
applications, not yet identified as possible EMI sensitive, to
be more robust for EMI.
INPUT CHARACTERISTICS
The input common mode voltage range of the LMV861 and
LMV862 includes ground, and can even sense well below
ground. The CMRR level does not degrade for input levels up
to 1.2V below the supply voltage. For a supply voltage of 5V,
the maximum voltage that should be applied to the input for
best CMRR performance is thus 3.8V.
When not configured as unity gain, this input limitation will
usually not degrade the effective signal range. The output is
rail-to-rail and therefore will introduce no limitations to the
signal range.
The typical offset is only 0.273 mV, and the TCV
0.7 μV/°C, specifications close to precision op amps.
CMRR MEASUREMENT
The CMRR measurement results may need some clarifica-
tion. This is because different setups are used to measure the
AC CMRR and the DC CMRR.
The DC CMRR is derived from ΔV
is stated in the tables, and is tested during production testing.
The AC CMRR is measured with the test circuit shown in
Figure 1.
OS
versus ΔV
CM
. This value
OS
is
13
The configuration is largely the usually applied balanced con-
figuration. With potentiometer P1, the balance can be tuned
to compensate for the DC offset in the DUT. The main differ-
ence is the addition of the buffer. This buffer prevents the
open-loop output impedance of the DUT from affecting the
balance of the feedback network. Now the closed-loop output
impedance of the buffer is a part of the balance. But as the
closed-loop output impedance is much lower, and by careful
selection of the buffer also has a larger bandwidth, the total
effect is that the CMRR of the DUT can be measured much
more accurately. The differences are apparent in the larger
measured bandwidth of the AC CMRR.
One artifact from this test circuit is that the low frequency CM-
RR results appear higher than expected. This is because in
the AC CMRR test circuit the potentiometer is used to com-
pensate for the DC mismatches. So, mainly AC mismatch is
all that remains. Therefore, the obtained DC CMRR from this
AC CMRR test circuit tends to be higher than the actual DC
CMRR based on DC measurements.
The CMRR curve in Figure 2 shows a combination of the AC
CMRR and the DC CMRR.
FIGURE 1. AC CMRR Measurement Setup
FIGURE 2. CMRR Curve
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