INA116UA - 3fA Ultra-Low Bias In-Amp SOIC-16 | Texas Instruments
MPN: INA116UA β Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $22.34 | $22.34 |
| 10 | $21.55 | $215.50 |
| 100 | $20.8 | $2,080.00 |
| 500 | $20.1 | $10,050.00 |
| 1,000 | $19.5 | $19,500.00 |
Drop-in alternatives for INA116UA β same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
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| Amplifier Type | Instrumentation Amplifier |
| Number of Channels | 1 |
| Input Bias Current | 3 fA typ at 25C |
| Input Bias Current at 85C | 25 fA |
| Input Offset Voltage | 2 mV max |
| Gain Range | 1 V/V to 1000 V/V (single external resistor) |
| Bandwidth | 800 kHz |
| Input Voltage Noise | 28 nV/sqrt(Hz) at 1 kHz |
| Supply Voltage Range | 9 V to 36 V total (dual or single supply) |
| Quiescent Current | 1 mA |
| Input Topology | Difet FET inputs with buffered guard drive |
| Guard Drive Pins | Yes (buffered, adjacent to both inputs) |
| Input Overvoltage Protection | Yes (internal) |
| Package | 16-SOIC (0.295 in, 7.50 mm width) |
| Mounting Type | Surface Mount |
INA116UA 16-soic (0.295 in, 7.50 mm width) Pin Configuration Guide
Complete pinout information for INA116UA (16-soic (0.295 in, 7.50 mm width) package) with Yes (buffered, adjacent to both inputs) pins. This analog component features input, output, and power supply pins. Refer to the manufacturer datasheet for offset null, compensation, and enable pin configurations. Ideal for signal conditioning and amplifier circuits.
No detailed pinout data available for INA116UA.
Refer to the datasheet for full pin configuration.
Estimated pin count: Yes (buffered, adjacent to both inputs) pins (analog package)
Safe Operating Area (SOA) & Thermal Characteristics
No official SOA curve available for this component. Always operate within absolute maximum ratings specified in the datasheet. Ensure adequate cooling and derate as needed.
Typical Applications
INA116UA is suitable for 6 applications: pH and Ion-Selective Electrode Measurement, Photodiode and Photomultiplier Monitoring, Capacitive and Piezoelectric Sensor Amplification, Precision Laboratory Electrometer and Picoammeter Front Ends, Medical and Biosignal Acquisition, Mass Spectrometry and Ion Chamber Signal Chains.
pH and Ion-Selective Electrode Measurement
Glass pH electrodes and ion-selective electrodes present source impedances from tens of megohms to over 1 GOhm, making input bias current the dominant error source in the analog front end. The INA116UA fits this application precisely: its 3 fA typical input bias current at 25C produces only microvolts of error even across a gigaohm electrode, and its 2 mV maximum offset is calibrated in system software. In a typical circuit, the electrode buffer output drives the differential inputs while the buffered guard pins boot-strap the coaxial cable shield and a PCB guard ring, forcing shield leakage to near zero. The 800 kHz bandwidth far exceeds the slow electrode response, so no speed is sacrificed for the femtoampere input performance.
Recommended
Photodiode and Photomultiplier Monitoring
Photodiodes operated in photovoltaic mode and photomultiplier tube anodes are current sources with very high dynamic impedance, so amplifier input bias current adds directly to the signal current and corrupts low-light measurements. The INA116UA addresses this with 3 fA typical input bias at 25C and 25 fA at 85C, three orders of magnitude below typical FET-input op amps, enabling detection of femtoampere-level photocurrents. The buffered guard drives are connected to the photodiode anode/cathode guard rings and cable shields to suppress surface leakage, which otherwise dominates the input current budget. Its three-op-amp topology allows gain from 1 to 1000 V/V with a single resistor, letting one design cover multiple optical power ranges without changing the input structure.
Recommended
Capacitive and Piezoelectric Sensor Amplification
Piezoelectric accelerometers, hydrophones, and capacitive sensors exhibit charge-output behavior with source capacitance in the picofarad-to-nanofarad range; any amplifier leakage or bias current drains the charge and produces drift. The INA116UA's Difet inputs with 3 fA bias current minimize this charge leakage, while its high input impedance preserves the sensor's low-frequency response. The guarded input structure is essential here: the buffered guard pins are tied to driven shields around the high-impedance node so that PCB surface leakage, typically far larger than the IC bias, is boot-strapped away. With 800 kHz bandwidth and single-resistor gain setting from 1 to 1000 V/V, the device supports both quasistatic pressure measurement and dynamic vibration signal chains.
Recommended
Precision Laboratory Electrometer and Picoammeter Front Ends
Electrometer-class instruments measuring current in the femtoampere-to-picoampere range or voltage from gigaohm sources require an input stage whose own bias current is negligible. The INA116UA serves as a differential electrometer front end: 3 fA input bias at 25C, internal input overvoltage protection for robustness against transients, and guard pins that implement the classic driven-guard technique used in laboratory electrometers. Its differential architecture rejects ground-loop and common-mode interference that plagues single-ended electrometer inputs, with high common-mode rejection. The 1 mA quiescent current and 9 V to 36 V supply range allow benchtop or battery-powered instrument designs, and gain programming with one resistor simplifies range switching in autoranging instruments.
Recommended
Medical and Biosignal Acquisition
Bioelectric signals such as EEG, ECG, and intracellular microelectrode potentials originate from very high source impedances - glass microelectrodes can exceed 100 MOhm - so front-end bias current directly distorts the recorded waveform. The INA116UA's 3 fA bias and buffered guard drives make it appropriate for research-grade microelectrode amplifiers and impedance-measurement channels, where it preserves signal fidelity that picoampere-class instrumentation amplifiers would compromise. Guard boot-strapping of electrode cables reduces mains hum pickup through shield leakage, improving common-mode performance in electrically noisy clinical environments. Designers must add isolation and defibrillation protection per applicable medical safety standards when the front end contacts patients; the INA116UA provides internal input overvoltage protection as a first layer.
Recommended
Mass Spectrometry and Ion Chamber Signal Chains
Ionization chambers, Faraday cups, and mass spectrometer detectors generate currents spanning femtoamperes to microamperes at extremely high source impedance. The INA116UA functions as the sensitive transimpedance or differential front end for the low-current decades: femtoampere input bias ensures the amplifier does not mask the smallest detectable ion current, and the guard-driven input structure suppresses leakage paths across connector insulators and PCB surfaces, which would otherwise shunt charge. With 28 nV/Hz input noise at 1 kHz and a single-resistor gain architecture, range-gain switching can be implemented with analog switches around RG without touching the protected input node. Its 9 V to 36 V supply tolerance and low 1 mA consumption suit both rack instruments and compact vacuum-system electronics.
Recommended
Recommended Products Summary
Engineering reference data for INA116UA β comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | INA116PA |
|---|---|---|
| Package | 16-SOIC (7.50 mm) | 16-DIP (different footprint - not drop-in) |
| Brand | Texas Instruments | Texas Instruments (same) |
| Input Bias Current (typ, 25C) | 3 fA | 3 fA (same die) |
| Input Offset Voltage (max) | 2 mV | 2 mV |
| Gain Range | 1 to 1000 V/V | 1 to 1000 V/V |
| Bandwidth | 800 kHz | 800 kHz |
| Supply Voltage Range | 9 V to 36 V total | 9 V to 36 V total |
| Quiescent Current | 1 mA | 1 mA |
| Mounting Type | Surface Mount | Through-Hole |
Key Differentiators
- Femtoampere input bias current with buffered guard drives (vs INA116PA)
- Guarded Difet input structure vs standard FET-input in-amps (vs INA128-class devices (different pinout))
- Single-resistor gain programming (vs INA116PA)
Design Notes
Implement driven guard rings on the PCB to realize the 3 fA input specification. Route the input traces as guarded islands: connect each INA116UA guard-drive pin to a copper ring surrounding its corresponding input trace and to the driven shield of the input cable. The guard buffers output the input common-mode potential, so leakage current across the ring-to-trace resistance is boot-strapped to nearly zero. Use high-insulation-resistance substrate material, clean flux residue thoroughly (no-clean flux can be slightly conductive), and consider conformal coating for humid environments.
Decouple both supplies with 0.1 uF ceramic capacitors placed within 2 mm of the SOIC-16 supply pins, plus a 2.2 uF to 10 uF bulk capacitor per rail. The INA116UA draws only 1 mA quiescent, so supply noise is more a signal-integrity issue than a thermal one; any ripple on the rails can couple into the 28 nV/Hz input-referred noise floor. Operate from well-regulated plus/minus supplies within the 9 V to 36 V total range, and avoid sharing the analog supply with digital loads without local LC filtering.
Two frequent mistakes: first, leaving the guard pins unconnected, which discards the guarding advantage and lets PCB leakage (typically picoamperes) dominate the input current; always drive them. Second, using a high-TCR or wirewound gain resistor RG with long traces - gain accuracy and stability depend on RG quality, and long traces pick up noise that is amplified by the first stage. Also respect the input overvoltage protection limits; the internal protection clamps fault conditions but sustained overvoltage above the supply rails must still be current-limited with an external series resistor.
Compliance Information
Compliance status must be verified on the official TI product page at ti.com/product/INA116 for ordering option INA116UA; the verified web data retrieved does not include explicit RoHS/REACH declarations.
