Application Information
BENEFITS OF THE LMV321/LMV358/LMV324
Size
The small footprints of the LMV321/LMV358/LMV324 pack-
ages save space on printed circuit boards, and enable the
design of smaller electronic products, such as cellular
phones, pagers, or other portable systems. The low profile of
the LMV321/LMV358/LMV324 make them possible to use in
PCMCIA type III cards.
Signal Integrity
Signals can pick up noise between the signal source and the
amplifier. By using a physically smaller amplifier package, the
LMV321/LMV358/LMV324 can be placed closer to the signal
source, reducing noise pickup and increasing signal integrity.
Simplified Board Layout
These products help you to avoid using long PC traces in your
PC board layout. This means that no additional components,
such as capacitors and resistors, are needed to filter out the
unwanted signals due to the interference between the long
PC traces.
Low Supply Current
These devices will help you to maximize battery life. They are
ideal for battery powered systems.
Low Supply Voltage
National provides guaranteed performance at 2.7V and 5V.
These guarantees ensure operation throughout the battery
lifetime.
Rail-to-Rail Output
Rail-to-rail output swing provides maximum possible dynamic
range at the output. This is particularly important when oper-
ating on low supply voltages.
Input Includes Ground
Allows direct sensing near GND in single supply operation.
Protection should be provided to prevent the input voltages
from going negative more than −0.3V (at 25°C). An input
clamp diode with a resistor to the IC input terminal can be
used.
Ease of Use and Crossover Distortion
The LMV321/LMV358/LMV324 offer specifications similar to
the familiar LM324. In addition, the new LMV321/LMV358/
LMV324 effectively eliminate the output crossover distortion.
The scope photos in Figure 1 and Figure 2 compare the output
swing of the LMV324 and the LM324 in a voltage follower
configuration, with V
S
= ± 2.5V and R
L
(= 2 kΩ) connected to
GND. It is apparent that the crossover distortion has been
eliminated in the new LMV324.
10006097
FIGURE 1. Output Swing of LMV324
10006098
FIGURE 2. Output Swing of LM324
CAPACITIVE LOAD TOLERANCE
The LMV321/LMV358/LMV324 can directly drive 200 pF in
unity-gain without oscillation. The unity-gain follower is the
most sensitive configuration to capacitive loading. Direct ca-
pacitive loading reduces the phase margin of amplifiers. The
combination of the amplifier's output impedance and the ca-
pacitive load induces phase lag. This results in either an
underdamped pulse response or oscillation. To drive a heav-
ier capacitive load, the circuit in Figure 3 can be used.
10006004
FIGURE 3. Indirectly Driving a Capacitive Load Using
Resistive Isolation
13 www.national.com
LMV321/LMV358/LMV324 Single/Dual/Quad
