Datasheet

LMV796, LMV797
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SNOSAU9D MARCH 2006REVISED MARCH 2013
APPLICATION INFORMATION
ADVANTAGES OF THE LMV796/LMV797
Wide Bandwidth at Low Supply Current
The LMV796 and LMV797 are high performance op amps that provide a unity gain bandwidth of 17 MHz while
drawing a low supply current of 1.15 mA. This makes them ideal for providing wideband amplification in portable
applications.
Low Input Referred Noise and Low Input Bias Current
The LMV796/LMV797 have a very low input referred voltage noise density (5.8 nV/Hz at 1 kHz). A CMOS input
stage ensures a small input bias current (100 fA) and low input referred current noise (0.01 pA/Hz). This is very
helpful in maintaining signal fidelity, and makes the LMV796 and LMV797 ideal for audio and sensor based
applications.
Low Supply Voltage
The LMV796 and the LMV797 have performance specified at 2.5V and 5V supply. The LMV796 family is
specified to be operational at all supply voltages between 2.0V and 5.5V, for ambient temperatures ranging from
40°C to 125°C, thus utilizing the entire battery lifetime. The LMV796 and LMV797 are also specified to be
operational at 1.8V supply voltage, for temperatures between 0°C and 125°C. This makes the LMV796 family
ideal for usage in low-voltage commercial applications.
RRO and Ground Sensing
Rail-to-rail output swing provides maximum possible dynamic range at the output. This is particularly important
when operating at low supply voltages. An innovative positive feedback scheme is used to boost the current drive
capability of the output stage. This allows the LMV796 and the LMV797 to source more than 40 mA of current at
1.8V supply. This also limits the performance of the LMV796 family as comparators, and hence the usage of the
LMV796 and the LMV797 in an open-loop configuration is not recommended. The input common-mode range
includes the negative supply rail which allows direct sensing at ground in single supply operation.
Small Size
The small footprint of the LMV796 and the LMV797 package saves space on printed circuit boards, and enables
the design of smaller electronic products, such as cellular phones, pagers, or other portable systems. Long
traces between the signal source and the op amp make the signal path susceptible to noise. By using the
physically smaller LMV796 or LMV797 package, the op amp can be placed closer to the signal source, reducing
noise pickup and increasing signal integrity.
CAPACITIVE LOAD TOLERANCE
The LMV796 and LMV797 can directly drive 120 pF 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, the circuit in
Figure 45 can be used.
In Figure 45, 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. Increased R
ISO
would, however, result in a reduced output swing and
short circuit current.
Figure 45. Isolation of C
L
to Improve Stability
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Product Folder Links: LMV796 LMV797