lm7341mfx National Semiconductor Corporation, lm7341mfx Datasheet - Page 14

• Manufacturer Part Number: lm7341mfx
• Description: Lm7341 Rail-to-rail Input/output ?15v, 4.6 Mhz Gbw, Operational Amplifier In Sot-23 Package
• Manufacturer: National Semiconductor Corporation

www.national.com
Application Information
GENERAL INFORMATION
Low supply current and wide bandwidth, greater than rail-to-
rail input range, full rail-to-rail output, good capacitive load
driving ability, wide supply voltage and low distortion all make
the LM7341 ideal for many diverse applications.
The high common-mode rejection ratio and full rail-to-rail in-
put range provides precision performance when operated in
non-inverting applications where the common-mode error is
added directly to the other system errors.
CAPACITIVE LOAD DRIVING
The LM7341 has the ability to drive large capacitive loads. For
example, 1000 pF only reduces the phase margin to about 30
degrees.
POWER DISSIPATION
Although the LM7341 has internal output current limiting,
shorting the output to ground when operating on a +30V pow-
er supply will cause the op amp to dissipate about 350 mW.
This is a worst-case example. In the 5-pin SOT-23 package,
the higher thermal resistance will cause a calculated rise of
113°C. This can raise the junction temperature to above the
absolute maximum temperature of 150°C.
Operating from split supplies greatly reduces the power dis-
sipated when the output is shorted. Operating on ±15V sup-
plies can only cause a temperature rise of 57°C in the 5-pin
SOT-23 package, assuming the short is to ground.
WIDE SUPPLY RANGE
The high power-supply rejection ratio (PSRR) and common
mode rejection ratio (CMRR) provide precision performance
when operated on battery or other unregulated supplies. This
advantage is further enhanced by the very wide supply range
(2.5V–32V) offered by the LM7341. In situations where highly
variable or unregulated supplies are present, the excellent
PSRR and wide supply range of the LM7341 benefit the sys-
tem designer with continued precision performance, even in
such adverse supply conditions.
THD+N vs. Frequency
20206053
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SPECIFIC ADVANTAGES OF 5-Pin SOT-23 (TinyPak)
The obvious advantage of the 5-pin SOT-23, TinyPak, is that
it can save board space, a critical aspect of any portable or
miniaturized system design. The need to decrease overall
system size is inherent in any handheld, portable, or
lightweight system application.
Furthermore, the low profile can help in height limited designs,
such as consumer hand-held remote controls, sub-notebook
computers, and PCMCIA cards.
An additional advantage of the tiny package is that it allows
better system performance due to ease of package place-
ment. Because the tiny package is so small, it can fit on the
board right where the op amp needs to be placed for optimal
performance, unconstrained by the usual space limitations.
This optimal placement of the tiny package allows for many
system enhancements, not easily achieved with the con-
straints of a larger package. For example, problems such as
system noise due to undesired pickup of digital signals can
be easily reduced or mitigated. This pick-up problem is often
caused by long wires in the board layout going to or from an
op amp. By placing the tiny package closer to the signal
source and allowing the LM7341 output to drive the long wire,
the signal becomes less sensitive to such pick-up. An overall
reduction of system noise results.
Often times system designers try to save space by using dual
or quad op amps in their board layouts. This causes a com-
plicated board layout due to the requirement of routing several
signals to and from the same place on the board. Using the
tiny op amp eliminates this problem.
Additional space savings parts are available in tiny packages
from National Semiconductor, including low power amplifiers,
precision voltage references, and voltage regulators.
LOW DISTORTION, HIGH OUTPUT DRIVE CAPABILITY
The LM7341 offers superior low-distortion performance, with
a total-harmonic-distortion-plus-noise of −66 dB at f = 10 kHz.
The advantage offered by the LM7341 is its low distortion
levels, even at high output current and low load resistance.