OPA131U - 4MHz 50pA FET Op Amp | Texas Instruments
MPN: OPA131U ✓ ActiveOPA131U Overview
An operational amplifier, or op amp, is an analog integrated circuit that amplifies the voltage difference between its inverting and non-inverting inputs. The OPA131 belongs to the FET-input operational-amplifier family, where the input stage uses field-effect-transistor biasing rather than a bipolar input stage. This topology is useful when the source presents high impedance, because input bias current can disturb the source voltage and distort the measurement.
The OPA131U combines a 4 MHz bandwidth with a 10 V/µs slew rate, according to the retrieved OPA131 data. Its maximum input offset voltage is 750 µV, and its input bias current is specified at no more than 50 pA. The wide supply range supports operation from ±18 V, while the low 750 µA power specification helps reduce system power when the amplifier operates across a broad range of analog signals.
The device is available in an 8-pin SOIC package and is part of the broader OPAx131 family, which also includes dual and quad versions in industry-standard pinouts. Its general-purpose characteristics make it suitable for sensor interfaces, transimpedance amplification, audio signal conditioning, instrumentation, and buffering. The 10 V/µs slew rate supports faster signal transitions than a low-bandwidth precision-only amplifier, while the 4 MHz bandwidth is useful for moderate-frequency analog paths.
OPA131U design decisions should focus on input-source impedance, supply voltage, output swing, noise requirements, and stability with capacitive loads. Because a single amplifier must be checked for bias-current effects and offset error, source resistance and bias-network resistance should be considered during input-stage design. The manufacturer product page and datasheet should be consulted for the complete electrical limits, pinout, and test conditions.
This product data combines verified manufacturer and distributor information with application guidance and source citations. Pricing, availability, lifecycle status, and detailed comparison values must be confirmed against the latest distributor records before purchasing or releasing a production design.
Drop-in alternatives for OPA131U — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with OPA131U (same form factor and footprint) — differing in Package, Series, Slew Rate.
OPA131UA
✅ Drop-In📋 Reference alternative (not in catalog)
OPA131UG4
✅ Drop-In📋 Reference alternative (not in catalog)
OPA132U
✅ Drop-InContact for price
View Datasheet →OPA130UA
✅ Drop-In📋 Reference alternative (not in catalog)
OPA131U Maximum Ratings & Electrical Characteristics
| Product Type | Single general-purpose operational amplifier |
| Input Stage | FET input |
| Gain-Bandwidth Product | 4 MHz |
| Maximum Input Bias Current | 50 pA |
| Typical Power Consumption | 750 µA |
| Maximum Input Offset Voltage | 750 µV |
| Slew Rate | 10 V/µs |
| Supply Range | ±18 V |
| Number of Amplifiers | 1 |
| Circuit Count | 1 circuit |
| Package | 8-pin SOIC |
| Mounting Type | Surface mount |
| Input Bias Current | 50 pA maximum |
| Input Offset Voltage | 750 µV maximum |
| Capacitive Load Drive | Excellent capacitive load drive |
| Series | OPAx131 |
| Related Versions | OPA131 single, OPA2131 dual, OPA4131 quad |
| Product Description | General-purpose FET-input operational amplifier |
OPA131U Pin Configuration
| Pin 1 | NC — Not connected or package-specific; verify against the current manufacturer datasheet |
| Pin 2 | IN- — Inverting input |
| Pin 3 | IN+ — Non-inverting input |
| Pin 4 | V- — Negative supply |
| Pin 5 | NC — Not connected or package-specific; verify against the current manufacturer datasheet |
| Pin 6 | OUT — Output |
| Pin 7 | V+ — Positive supply |
| Pin 8 | NC — Not connected or package-specific; verify against the current manufacturer datasheet |
Typical Applications
OPA131U is suitable for 6 applications: High-Impedance Sensor Signal Conditioning, General-Purpose Analog Buffering, Audio and Low-Level Analog Signal Paths, Instrumentation and Measurement Front Ends, Active Filtering and Signal Conditioning, Portable and Low-Power Analog Systems.
High-Impedance Sensor Signal Conditioning
OPA131U fits high-impedance sensor front ends because its verified maximum input bias current is 50 pA, reducing the current that a resistive sensor node must supply. The single FET-input amplifier can buffer the sensor before a downstream ADC or instrumentation stage, while its 4 MHz gain-bandwidth product handles moderate-frequency signal paths. The 750 µV maximum input offset is useful when the sensor output is small, although the complete offset and drift specification should be checked under the actual supply and temperature conditions.
Recommended
General-Purpose Analog Buffering
OPA131U can serve as a voltage buffer when a high-impedance source must drive a longer trace or a following circuit without excessive loading. Its 50 pA maximum input bias current helps preserve source accuracy, and the 10 V/µs slew rate provides useful large-signal response for moderate-speed analog signals. The 4 MHz gain-bandwidth product makes the device appropriate for broad general-purpose buffering rather than only ultra-low-frequency precision applications.
Recommended
Audio and Low-Level Analog Signal Paths
OPA131U is usable in audio and low-level analog conditioning where the input source has appreciable impedance and the design benefits from low bias current. Its 10 V/µs slew rate is substantially higher than that of many precision-only amplifiers, while the 4 MHz bandwidth supports moderate-frequency content. Noise and distortion should be evaluated at the actual gain, load, and supply conditions because the verified data establishes general dynamic characteristics but does not provide the complete noise spectrum.
Recommended
Instrumentation and Measurement Front Ends
OPA131U can be used in instrumentation front ends when the sensor or reference node requires low input bias and the signal bandwidth is moderate. The single amplifier may be configured for non-inverting gain, inverting gain, differential-related buffering, or active filtering. Its 750 µV maximum input offset and 10 V/µs slew rate provide a practical balance, but precision measurements should verify offset drift, input common-mode range, output swing, and noise over the full required temperature range.
Recommended
Active Filtering and Signal Conditioning
OPA131U is suitable for active-filter stages where moderate signal bandwidth, acceptable slew rate, and low input bias current are required. The 4 MHz gain-bandwidth product provides design margin for small-signal filter poles, while the 10 V/µs slew rate helps preserve large-signal transitions. Component tolerances, noise gain, feedback capacitor selection, and stability with the intended load must be evaluated during design because the available verified data does not specify a complete filter application circuit.
Recommended
Portable and Low-Power Analog Systems
OPA131U's verified 750 µA power specification makes it relevant to portable analog systems where each amplifier's supply current contributes to the overall power budget. The low-bias input stage is useful with resistive sensors and battery-powered sensing nodes, while the 4 MHz bandwidth provides more performance than a purely DC-oriented general-purpose amplifier. Actual battery-life benefit depends on supply voltage, duty cycle, load, quiescent-current conditions, and the number of active amplifiers.
Recommended
Recommended Products Summary
Engineering reference data for OPA131U — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | OPA131UA | OPA131UG4 | OPA132U | OPA130UA |
|---|---|---|---|---|---|
| Package | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC | 8-pin SOIC |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Amplifier Type | Single general-purpose FET-input operational amplifier | OPA131 family single amplifier | OPA131 family single amplifier | OPA132 family amplifier | OPA130 family amplifier |
Key Differentiators
- Low-bias general-purpose FET input stage (vs OPA130UA)
- 4 MHz bandwidth with 10 V/µs slew rate (vs OPA132U)
- 8-pin SOIC family footprint (vs OPA131UA)
Design Notes
For high-impedance sources, begin with the verified 50 pA maximum input bias current rather than assuming the amplifier contributes no loading. Bias-current error is approximately equal to input bias current multiplied by source resistance, so even a small current can shift a high-value sensor node. Keep source impedances and feedback resistors practical, verify leakage from PCB contamination and humidity, and confirm the input common-mode range for the selected supply. This is especially important for electrostatic sensors, photodiode-style interfaces, and long high-impedance analog nodes.
The OPA131 family is described as having excellent capacitive load drive, but the actual circuit still requires a stability check. Keep the feedback loop short, place compensation and feedback components close to the device, and add a small isolation resistor between the amplifier output and unusually capacitive loads when required. Because the verified data does not provide the full load-versus-frequency stability graph, evaluate the actual cable, sensor, ADC input, and scope capacitance before production release.
Use short, guarded analog traces for OPA131U inputs and route high-impedance nodes away from switching nodes, clocks, inductors, and power-converter outputs. The 4 MHz gain-bandwidth product and 10 V/µs slew rate make the device useful for moderate-frequency signals, but they do not eliminate susceptibility to high-frequency coupled noise. A solid ground plane, clean supply bypassing, controlled impedance where appropriate, and careful grounding of downstream converters are more valuable than relying on amplifier bandwidth alone.
Compliance Information
The verified web data confirms the Texas Instruments product and distributor pages but does not provide explicit RoHS, REACH, lead-free, halogen-free, conflict-minerals, or automotive qualification statements for OPA131U.