LMP2021MAEVAL National Semiconductor, LMP2021MAEVAL Datasheet - Page 12

• Manufacturer Part Number: LMP2021MAEVAL
• Description: BOARD EVAL FOR LMP2021 OP AMP
• Manufacturer: National Semiconductor
• Series: LMP®r

Specifications of LMP2021MAEVAL

• Channels Per Ic: 1 - Single
• Amplifier Type: Instrumentation
• Output Type: Differential
• Slew Rate: 2.6 V/µs
• Current - Output / Channel: 50mA
• Operating Temperature: -40°C ~ 125°C
• Current - Supply (main Ic): 1.1mA
• Voltage - Supply, Single/dual (±): 2.2 V ~ 5.5 V
• Board Type: Fully Populated
• Utilized Ic / Part: LMP2021
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• -3db Bandwidth: -

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Application Information
LMP2021/LMP2022
The LMP2021/LMP2022 are single and dual precision oper-
ational amplifiers with ultra low offset voltage, ultra low offset
voltage drift, and very low input voltage noise with no 1/f and
extended supply voltage range. The LMP2021/LMP2022 of-
fer on chip EMI suppression circuitry which greatly enhances
the performance of these precision amplifiers in the presence
of radio frequency signals and other disturbances.
The LMP2021/LMP2022 utilize proprietary techniques to
measure and continuously correct the input offset error volt-
age. The LMP2021/LMP2022 have a DC input offset voltage
with a maximum value of ±5 μV and an input offset voltage
drift maximum value of 0.02 µV/°C. The input voltage noise of
the LMP2021/LMP2022 is less than 11 nV/
gain of 1000 V/V and has no flicker noise component. This
makes the LMP2021/LMP2022 ideal for high accuracy, low
frequency applications where lots of amplification is needed
and the input signal has a very small amplitude.
The proprietary input offset correction circuitry enables the
LMP2021/LMP2022 to have superior CMRR and PSRR per-
formances. The combination of an open loop voltage gain of
160 dB, CMRR of 142 dB, PSRR of 130 dB, along with the
ultra low input offset voltage of only −0.4 µV, input offset volt-
age drift of only −0.004 µV/°C, and input voltage noise of only
260 nV
great choices for high gain transducer amplifiers, ADC buffer
amplifiers, DAC I-V conversion, and other applications re-
quiring precision and long-term stability. Other features are
rail-to-rail output, low supply current of 1.1 mA per amplifier,
and a gain-bandwidth product of 5 MHz.
The LMP2021/LMP2022 have an extended supply voltage
range of 2.2V to 5.5V, making them ideal for battery operated
portable applications. The LMP2021 is offered in 5-pin
SOT-23 and 8-pin SOIC packages. The LMP2022 is offered
in 8-pin MSOP and 8-Pin SOIC packages.
EMI SUPPRESSION
The near-ubiquity of cellular, bluetooth, and Wi-Fi signals and
the rapid rise of sensing systems incorporating wireless ra-
dios make electromagnetic interference (EMI) an evermore
important design consideration for precision signal paths.
Though RF signals lie outside the op amp band, RF carrier
switching can modulate the DC offset of the op amp. Also
some common RF modulation schemes can induce down-
converted components. The added DC offset and the induced
signals are amplified with the signal of interest and thus cor-
rupt the measurement. The LMP2021/LMP2022 use on chip
filters to reject these unwanted RF signals at the inputs and
power supply pins; thereby preserving the integrity of the pre-
cision signal path.
Twisted pair cabling and the active front-end’s common-mode
rejection provide immunity against low frequency noise (i.e.
60 Hz or 50 Hz mains) but are ineffective against RF interfer-
ence. Figure 12 displays this. Even a few centimeters of PCB
trace and wiring for sensors located close to the amplifier can
pick up significant 1 GHz RF. The integrated EMI filters of
LMP2021/LMP2022 reduce or eliminate external shielding
and filtering requirements, thereby increasing system robust-
ness. A larger EMIRR means more rejection of the RF inter-
ference. For more information on EMIRR, please refer to
AN-1698.
PP
at 0.1 Hz to 10 Hz make the LMP2021/LMP2022
at a voltage
12
INPUT VOLTAGE NOISE
The input voltage noise density of the LMP2021/LMP2022
has no 1/f corner, and its value depends on the feedback net-
work used. This feature of the LMP2021/LMP2022 differenti-
ates this family from other products currently available from
other vendors. In particular, the input voltage noise density
decreases as the closed loop voltage gain of the LMP2021/
LMP2022 increases. The input voltage noise of the LMP2021/
LMP2022 is less than 11 nV/
age gain of the op amp is 1000. Higher voltage gains are
required for smaller input signals. When the input signal is
smaller, a lower input voltage noise is quite advantageous
and increases the signal to noise ratio.
Figure 1 shows the input voltage noise of the LMP2021/
LMP2022 as the closed loop gain increases.
Figure 2 shows the input voltage noise density does not have
the 1/f component.
With smaller and smaller input signals and high precision ap-
plications with lower error budget, the reduced input voltage
noise and no 1/f noise allow more flexibility in circuit design.
FIGURE 1. Input Voltage Noise Density decreases with
FIGURE 2. Input Voltage Noise Density with no 1/f
Gain
when the closed loop volt-
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