LMV921EVAL National Semiconductor, LMV921EVAL Datasheet - Page 17

• Manufacturer Part Number: LMV921EVAL
• Description: EVALUATION BOARD FOR LMV921
• Manufacturer: National Semiconductor

Specifications of LMV921EVAL

• Channels Per Ic: 1 - Single
• Amplifier Type: General Purpose
• Output Type: Single-Ended, Rail-to-Rail
• Slew Rate: 0.45 V/µs
• Current - Output / Channel: 98mA
• Operating Temperature: -40°C ~ 85°C
• Current - Supply (main Ic): 160µA
• Voltage - Supply, Single/dual (±): 1.5 V ~ 5 V
• Board Type: Fully Populated
• Utilized Ic / Part: LMV921
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Other names: *LMV921EVAL

Application Note
the amplifier becomes a function of the input common mode
voltage and has a crossover point at 1V below V
in the V
This V
and AC coupled signals if proper care is not taken. For large
input signals that include the V
dynamic range, this will cause distortion in the output signal.
One way to avoid such distortion is to keep the signal away
from the crossover. For example, in a unity gain buffer
configuration and with V
contain input-crossover distortion while a 3V peak-to-peak
signal centered at 1.5V will not contain input-crossover dis-
tortion as it avoids the crossover point. Another way to avoid
large signal distortion is to use a gain of −1 circuit which
avoids any voltage excursions at the input terminals of the
amplifier. In that circuit, the common mode DC voltage can
be set at a level away from the V
For small signals, this transition in V
dependent spurious signal in series with the input signal and
can effectively degrade small signal parameters such as
gain and common mode rejection ratio. To resolve this prob-
lem, the small signal should be placed such that it avoids the
V
In addition to the rail-to-rail performance, the output stage
can provide enough output current to drive 600
Because of the high current capability, care should be taken
not to exceed the 150˚C maximum junction temperature
specification.
5.0 Power-Supply Considerations
The LMV921/LMV922/LMV924 are ideally suited for use with
most battery-powered systems. The LMV921/LMV922/
OS
crossover point.
OS
OS
crossover point can create problems for both DC
vs. V
CM
curves.
S
Battery Type
= 5V, a 5V peak-to-peak signal will
Ni - Cad
Alkaline
Lithium
NMH
TABLE 1. LMV921 Characteristics with Typical Battery Systems.
(Continued)
OS
OS
crossover point in their
OS
cross-over point.
shows up as a V
Voltage (V)
Operating
1.5
2.7
1.2
1.2
+
as shown
loads.
CM
End-of-Life
Voltage (V)
0.9
2.0
0.9
1.0
17
LMV924 operate from a single +1.8V to +5.0V supply and
consumes about 145µA of supply current per Amplifier. A
high power supply rejection ratio of 78dB allows the amplifier
to be powered directly off a decaying battery voltage extend-
ing battery life.
Table 1 lists a variety of typical battery types. Batteries have
different voltage ratings; operating voltage is the battery
voltage under nominal load. End-of-Life voltage is defined as
the voltage at which 100% of the usable power of the battery
is consumed. Table 1 also shows the typical operating time
of the LMV921.
6.0 Distortion
The two main contributors of distortion in LMV921/LMV922/
LMV924 family is:
1. Output crossover distortion occurs as the output transi-
tions from sourcing current to sinking current.
2. Input crossover distortion occurs as the input switches
from NPN to PNP transistor at the input stage.
To decrease crossover distortion:
1. Increase the load resistance. This lowers the output cross-
over distortion but has no effect on the input crossover
distortion.
2. Operate from a single supply with the output always
sourcing current.
3. Limit the input voltage swing for large signals between
ground and one volt below the positive supply.
4. Operate in inverting configuration to eliminate common
mode induced distortion.
5. Avoid small input signal around the input crossover region.
The discontinuity in the offset voltage will effect the gain,
CMRR and PSRR.
Size (mA - h)
Capacity AA
1000
1000
375
500
time (Hours)
Operating
LMV921
6802
6802
2551
3401
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