LMP2234AMT/NOPB National Semiconductor, LMP2234AMT/NOPB Datasheet - Page 15

• Manufacturer Part Number: LMP2234AMT/NOPB
• Description: IC AMP PREC QUAD LO PWR 14TSSOP
• Manufacturer: National Semiconductor
• Series: LMP®, PowerWise®r

Specifications of LMP2234AMT/NOPB

• Amplifier Type: General Purpose
• Number Of Circuits: 4
• Output Type: Rail-to-Rail
• Slew Rate: 0.058 V/µs
• Gain Bandwidth Product: 130kHz
• Current - Input Bias: 0.02pA
• Voltage - Input Offset: 10µV
• Current - Supply: 36µA
• Current - Output / Channel: 30mA
• Voltage - Supply, Single/dual (±): 1.6 V ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -
• Other names: *LMP2234AMT; *LMP2234AMT/NOPB; LMP2234AMT

Application Information
LMP2234
The LMP2234 is a quad CMOS precision amplifier that offers
low offset voltage, low offset voltage drift, and high gain while
consuming less than 10 μA of supply current per channel.
The LMP2234 is a micropower op amp, consuming only
36 μA of current. Micropower op amps extend the run time of
battery powered systems and reduce energy consumption in
energy limited systems. The guaranteed supply voltage range
of 1.8V to 5.5V along with the ultra-low supply current extend
the battery run time in two ways. The extended power supply
voltage range of 1.8V to 5.5V enables the op amp to function
when the battery voltage has depleted from its nominal value
down to 1.8V. In addition, the lower power consumption in-
creases the life of the battery.
The LMP2234 has input referred offset voltage of only ±150
μV maximum at room temperature. This offset is guaranteed
to be less than ±230 μV over temperature. This minimal offset
voltage along with very low TCV
allows more accurate signal detection and amplification in
precision applications.
The low input bias current of only ±20 fA gives the LMP2234
superiority for use in high impedance sensor applications.
Bias current of an amplifier flows through source resistance
of the sensor and the voltage resulting from this current flow
appears as a noise voltage on the input of the amplifier. The
low input bias current enables the LMP2234 to interface with
high impedance sensors while generating negligible voltage
noise. Thus the LMP2234 provides better signal fidelity and
a higher signal-to-noise ratio when interfacing with high
impedance sensors.
National Semiconductor is heavily committed to precision
amplifiers and the market segments they serve. Technical
support and extensive characterization data is available for
sensitive applications or applications with a constrained error
budget.
The operating voltage range of 1.8V to 5.5V over the exten-
sive temperature range of −40°C to 125°C makes the
LMP2234 an excellent choice for low voltage precision appli-
cations with extensive temperature requirements.
The LMP2234 is offered in the 14-pin TSSOP and 14-pin
SOIC package. These small packages are ideal solutions for
area constrained PC boards and portable electronics.
TOTAL NOISE CONTRIBUTION
The LMP2234 has very low input bias current, very low input
current noise, and low input voltage noise for micropower
amplifiers. As a result, this amplifier makes a great choice for
circuits with high impedance sensor applications.
shows the typical input noise of the LMP2234 as a function of
source resistance at f = 1 kHz where:
•
•
•
•
e
e
referred current noise or e
e
e
n
i
t
ni
is the voltage drop across source resistance due to input
shows the thermal noise of the source resistance
denotes the input referred voltage noise
shows the total noise on the input.
i
= R
OS
S*
of only 0.3 µV/°C typical
i
n
15
Where:
The input current noise of the LMP2234 is so low that it will
not become the dominant factor in the total noise unless
source resistance exceeds 300 MΩ, which is an unrealisti-
cally high value. As is evident in Figure 1, at lower R
total noise is dominated by the amplifier’s input voltage noise.
Once R
becomes the thermal noise of R
current noise will not be the dominant noise factor for any
practical application.
VOLTAGE NOISE REDUCTION
The LMP2234 has an input voltage noise of 60 nV/
this value is very low for micropower amplifiers, this input
voltage noise can be further reduced by placing multiple am-
plifiers in parallel as shown in Figure 2. The total voltage noise
on the output of this circuit is divided by the square root of the
number of amplifiers used in this parallel combination. This is
because each individual amplifier acts as an independent
noise source, and the average noise of independent sources
is the quadrature sum of the independent sources divided by
the number of sources. For N identical amplifiers, this means:
S
is larger than 100 kΩ, then the dominant noise factor
FIGURE 1. Total Input Noise
S
. As mentioned before, the
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S
values,
. While