Datasheet

LMV721-N, LMV722-N
www.ti.com SNOS414I –AUGUST 1999–REVISED AUGUST 2013
APPLICATION NOTES
BENEFITS OF THE LMV721-N/722 SIZE
The small footprints of the LMV721-N/722 packages 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
LMV721-N/722 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 LMV721-N/722 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 CurrentThese devices will help you to maximize battery life. They are ideal for battery powered
systems.
Low Supply Voltage TI provides ensured performance at 2.2V and 5V. These specifications 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 operating 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.
CAPACITIVE LOAD TOLERANCE
The LMV721-N/722 can directly drive 4700pF in unity-gain without oscillation. The unity-gain follower is the most
sensitive configuration to capacitive loading. Direct capacitive loading reduces the phase margin of amplifiers.
The combination of the amplifier's output impedance and the capacitive load induces phase lag. This results in
either an underdamped pulse response or oscillation. To drive a heavier capacitive load, circuit in Figure 23 can
be used.
Figure 23. Indirectly Driving A capacitive Load Using Resistive Isolation
In Figure 23, the isolation resistor R
ISO
and the load capacitor C
L
form a pole to increase stability by adding more
phase margin to the overall system. the desired performance depends on the value of R
ISO
. The bigger the R
ISO
resistor value, the more stable V
OUT
will be. Figure 24 is an output waveform of Figure 23 using 100kΩ for R
ISO
and 2000µF for C
L
.
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Product Folder Links: LMV721-N LMV722-N