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Precision op amps are defined by a combination of low offset, low noise, high open-loop gain, and specialized topologies. This page provides you with various tools to help you select the right amplifier for your application.
Quick Links to Parametric Table (After clicking a link below, click on the yellow highlighted column to sort) |
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Multi-Purpose Op Amp Quick Selector
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You can also view these parts in a parametric table
You can also view these parts in a parametric table
Offset and noise of amplifiers limit (to a first order) the accuracy and resolution of a precision system. Although today's intelligent systems can calibrate out DC system errors such as the amplifier's offset, this improvement in baseline accuracy comes at the expense of dynamic range (resolution). Noise, on the other hand, cannot be calibrated out of a signal path and thus directly degrades the system's resolution or sensitivity. The high gain required in front-end stages dictates careful selection of amplifiers for their input-referred voltage and current properties.
The "By Lowest Noise" graph serves as a starting point for the designer to quickly choose an amplifier based on flat-band noise density, the dominant contributor in most applications. For clarity, only a selection of op amps suitable for precision applications is shown in the graphs below. Singles, duals, and quads may be found by clicking on the part.
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Peak-to-peak voltage noise at the output can be estimated by 6.6 x voltage noise density x rt-bandwidth x gain. Thus, the larger the amplification, the more noise density matters for high resolution systems. Low noise amplifiers are also critical for processing very small signals.
Current noise is converted to voltage noise by the feedback network. In photodiode and other applications relying on high transimpedance gain, low current noise op-amps such as LMC662 and LMC6081 are preferred, even at the expense of higher input voltage noise densities. For instance, a 1M-ohm transimpedance translates 10 fA/rt-Hz current noise into equivalent 10 nV/rt-Hz voltage noise.
On the other hand, low valued resistors in the feedback path allow for higher current noise op amps such as LMH6624 and LMP7731 to be used to create the absolutely lowest noise front-ends when power consumption is a lesser consideration. However, the LMP7731 has a 1/f noise corner in the single Hz range (5 decades lower than the LMH6624), making it more appropriate for the majority of precision sensing applications.
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Amplifiers with lower Vos and Ib allow for more of the output range to be allocated to the signal, thereby improving system resolution. To aid the system designer with bounded error budgets, National guarantees the maximum Vos and Ib through rigorous testing in production.
Input offset voltage considerations
For preamplifier with gain of 500, a +-1mV offset translates to +-500mV at its output. This amount represents 17% of a 3V signal path. Thus when system dynamic range is important, the first step in picking an amplifier is to choose one with low offset voltage.
Input bias current considerations
Large resistor values are often employed in today's distributed sensing and portable systems to conserve power. These impedances in the feedback network convert an op amp's input bias currents into offset voltages, and same concerns of the preceding paragraphs apply. 1uA of Ib translates to 1mV of effective Vos with 1K-ohm equivalent impedances. Thus the system designer should also favor amplifiers with low input bias current.
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Some highlights:
- achieves best-in-class offset using zero-drift technology. It is a member of National's EMI-Hardened EMIRR family.
- offers an excellent balance between noise, offset, bandwidth, and power. It is a member of National's EMIRR family.
- and represent the best noise performance under 200uA supply current.
- is the lowest power low-offset op amp from National. Consuming just 16uW, it can run for 2 years continuously from a coin cell.
- has enable/disable in a 6pin SOT-23 and comes in a decompensated version () and 5pin SOT-23 ()
- also comes in a decompensated version, .
Historically, low noise has been associated with amplifiers requiring high supply voltages. With the introduction of National's proprietary VIP50 process, low noise became available at lower operating voltages as well. Coupled with low supply currents, the LMP and LMV families enable a new class of portable precision.
Low supply currents are critical for applications powered either by a battery or from energy harvesting. The "By Operating Voltage" and "By Supply Current" graphs offer the design engineer a broad portfolio from which to choose the lowest noise op amp for any power budget.
For clarity, only a selection of op amps suitable for precision applications is shown on the selection graphs on this page. Singles are shown on the graph, but duals and quads may be found by clicking on the part in the graph and checking the "Also Recommended" field on the product page.
Precision Amplifiers by End Market
Precision is a summation of various DC and AC parameters (e.g. low noise, low offset voltage, low input bias current and other application dependent parameters) and National optimizes these requirements for a wide variety of precision applications. The tables below highlight some of National's industry-leading precision amplifier products by end application. Many National Op Amps are tested at three temperatures to ensure consistent performance to specification.
Automotive Precision Op Amps
Automotive applications, such as crash detection, active noise cancellation, and navigation, require low offset voltage, low input bias current, and low offset voltage drift at a high voltage supply range. National offers an increasing number of AEC-Q100-compliant devices. National also has the only current sense operational amplifiers which have tested performance over temperature. National provides the latest solutions making automobiles more efficient, safer, and greener.
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Vmin |
Vmax |
Vos (max) |
TCVos |
Ib |
Rail-to-Rail |
Features |
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2.7 V |
12 V |
0.2 mV |
1 µV/°C |
0.2 pA |
Input/Output |
Sensor interface, current sensing (ECU and other motor control) applications |
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4.75 V |
5.5 V |
1 mV |
6 µV/°C |
20 pA |
Output |
Current sense with fixed gain of 20 to drive an ADC to full scale, 100% tri-temp tested |
Industrial Precision Op Amps
Industrial applications, such as sensing & detection, weigh scales, pressure monitoring, and motor control, require adjustable gain and low gain error. Reliability, efficiency and low power consumption are key factors that make National's precision amplifiers a great choice for industrial needs.
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Vmin |
Vmax |
Vos (max) |
TCVos |
Gain |
Gain Error (max) |
Rail-to-Rail |
Features |
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2.7 V |
5.5 V |
250 µV |
1.5 µV/°C |
1 V/V to 16 V/V |
0.03% |
Input/Output |
Precision Gain Block for industrial instrumentation and Built-In Test Equipment (BITE) |
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2.2 V |
5.5 V |
5 µV |
0.004 µV/°C |
160 dB |
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Input/Output |
Excellent 11nV/vHz at a gain of 1000V/V for load, force, and pressure sensor applications. This zero drift op amp has no 1/f flicker noise component. |
Consumer/Portable Precision Op Amps
Consumer applications, such as notebook PCs, Bluetooth headsets, and portable media players, require low power consumption. EMI-hardened amplifiers resist interference from mobile phones and other wireless devices while maintaining accurate operation. With National's PowerWise products, sound, display, and power-efficiency are enhanced in consumer and portable electronics.
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Vmin |
Vmax |
EMIRR |
Is |
Vos (max) |
TCVos (max) |
Ib (max) |
Features |
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2.7 V |
5.5 V |
120 dB |
0.24 mA |
1 mV |
1.5 µV/°C |
1 pA |
Low power and EMI-hardened |
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2.7 V |
5.5 V |
89 dB |
0.52 mA |
1 mV |
2 µV/°C |
10 pA |
Low power and EMI-hardened |
Medical Precision Op Amps
Medical applications, such as blood pressure monitors, dialysis machines, and portable medical instruments, require low noise, low offset voltage, high CMRR, and rail-to-rail input and output. National's high performance precision products offer the latest solutions for accurate and reliable medical applications.
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Vmin |
Vmax |
Vos (max) |
CMRR (min) |
Noise |
Features |
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1.8 V |
5.5 V |
500 µV |
105 dB |
3.3 nV/vHz |
Low 3.3nV/vHz noise at 3Hz. Ideal for precision, low noise, low voltage applications. |
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1.6 V |
5.5 V |
150 µV |
81 dB |
60 nV/vHz |
Ideal for portable instrumentation |
Instrumentation Precision Op Amps
Instrumentation applications, such as data acquisition, digital storage scopes and spectrum analyzers require low offset voltage, high CMRR and high PSRR. National offers an extensive portfolio of amplifiers for metrology applications that meet instrumentation standards, including electrometer amplifiers, amplifiers for transimpedance circuits, chopper amplifiers and auto-zero amplifiers.
Featured Product
- - Zero-Drift, Programmable Instrumentation Amplifier with Diagnostics
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Vmin |
Vmax |
Vos (max) |
GBP |
CMRR (min) |
PSRR (min) |
Rail-to-Rail |
Features |
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1.8 V |
5.5 V |
50 µV |
3 MHz |
100 dB |
95 dB |
Input/Output |
Auto zero. Precision and long term stability. No 1/f noise. |
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2.7 V |
12 V |
200 µV |
2.5 MHz |
88 dB |
86 dB |
Input/Output |
CMOS input stage and wide supply voltage range |
Useful Links
Sensing & Detection Application Diagrams
Automotive Application Diagrams
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