INA111AP - High-Speed FET-Input Instrumentation Amplifier | Texas Instruments
MPN: INA111AP ✓ ActiveINA111AP Overview
An instrumentation amplifier is a precision amplifier designed to amplify small differential signals while rejecting large common-mode voltages. Its internal differential amplifier stages provide accurate gain, high input impedance, and balanced inputs, making the category well suited to sensor bridges, strain gauges, biomedical instrumentation, and industrial measurement systems. Within the signal-chain hierarchy, the INA111AP belongs to the amplifier IC family and specifically serves as a differential instrumentation amplifier.
A single external resistor sets the closed-loop gain, simplifying adjustment while preserving the performance of the internal current-feedback architecture. The gain can range from 1 to over 1,000 V/V, allowing the same device to amplify millivolt-level sensor outputs or larger instrumentation signals. Laser trimming supports low offset voltage, with a maximum of 500 µV, and maximum offset-voltage drift of 5 µV/°C.
The current-feedback topology extends bandwidth to 2 MHz at a gain of 10 and provides a settling time of 4 µs to 0.01% at a gain of 100. These speed characteristics make the INA111AP suitable for measurement systems that need better transient response than conventional voltage-feedback instrumentation amplifiers, although bandwidth decreases as the selected gain increases.
Typical applications include precision bridge excitation and readout, low-current sensor interfaces, laboratory instrumentation, diagnostic equipment, and industrial control systems. The wide supply range of 12 V to 36 V supports higher-voltage industrial systems, while the FET-input architecture minimizes input-bias-current error when measuring high-impedance sources.
For reliable circuit implementation, place the gain-setting resistor close to the RG pins, provide stable input and output decoupling, and keep sensitive input traces away from high-current switching paths. Verify settling time and bandwidth at the actual selected gain because both performance characteristics depend on gain, supply voltage, and signal amplitude.
This page combines manufacturer specifications, package and pin guidance, application engineering notes, and drop-in replacement analysis to support faster component selection and PCB implementation. It identifies where the INA111AP fits in measurement systems and clarifies the practical limits engineers should check before finalizing a precision signal chain.
Drop-in alternatives for INA111AP — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
No drop-in alternatives available for this product.
Request AlternativesINA111AP Maximum Ratings & Electrical Characteristics
| Product Type | High-speed FET-input instrumentation amplifier |
| Number of Circuits | 1 circuit |
| Architecture | Current-feedback instrumentation amplifier |
| Input Bias Current | 20 pA maximum |
| Input Offset Voltage | 500 µV maximum |
| Input Offset Voltage Drift | 5 µV/°C maximum |
| Common-Mode Rejection | 106 dB minimum |
| Bandwidth at Gain 10 | 2 MHz |
| Settling Time | 4 µs to 0.01% at gain 100 |
| Gain Range | 1 to over 1,000 V/V |
| Gain Setting | 1 external resistor |
| Supply Voltage Range | 12 V to 36 V |
| Maximum Supply Voltage | 36 V |
| Minimum Supply Voltage | 12 V |
| Package | 8-pin plastic DIP |
| Mounting Type | Through-hole |
INA111AP Pin Configuration
| Pin 1 | RG — Gain-setting resistor connection |
| Pin 2 | -IN — Inverting input |
| Pin 3 | +IN — Non-inverting input |
| Pin 4 | V- — Negative supply connection |
| Pin 5 | REF — Reference input |
| Pin 6 | OUT — Amplified output |
| Pin 7 | V+ — Positive supply connection |
| Pin 8 | RG — Gain-setting resistor connection |
Typical Applications
INA111AP is suitable for 6 applications: Precision Bridge Sensor Readout, High-Impedance Transducer Interface, Laboratory Instrumentation Front End, Medical and Diagnostic Signal Conditioning, Industrial Process Measurement, Rapid Data-Acquisition Front End.
Precision Bridge Sensor Readout
The INA111AP fits precision bridge measurements because it amplifies small differential sensor voltages while its 106 dB minimum common-mode rejection suppresses common-mode error. With gain set from 1 to over 1,000 V/V, the amplifier can bring a millivolt-level bridge output into a measurable range without requiring multiple discrete gain stages. Place the gain resistor close to the RG pins and keep the bridge return path away from switching nodes; at gain 10, the device reaches 2 MHz bandwidth, providing useful response beyond static Wheatstone-bridge measurements.
Recommended
High-Impedance Transducer Interface
The INA111AP is appropriate for high-impedance transducers because its FET inputs limit input bias current to 20 pA maximum. Combined with gains from 1 to over 1,000 V/V, this reduces loading error in capacitive or electrostatic sensor measurements. The 500 µV maximum offset and 5 µV/°C maximum drift remain important for DC accuracy, while the 4 µs settling time to 0.01% at gain 100 supports faster acquisition sequences. Shield sensitive inputs and control PCB contamination to preserve the practical benefit of the low-bias architecture.
Recommended
Laboratory Instrumentation Front End
The INA111AP provides a compact front end for laboratory instrumentation that must measure small differential signals over a broad frequency range. Its current-feedback architecture delivers 2 MHz bandwidth at gain 10, and gain 100 settling reaches 0.01% in 4 µs. A single external resistor selects gain from 1 to over 1,000 V/V, simplifying instrument configuration. Use the 8-pin plastic DIP package for prototypes and manually serviced boards, and validate the complete acquisition chain because amplifier settling and source impedance can affect the final acquisition accuracy.
Recommended
Medical and Diagnostic Signal Conditioning
The INA111AP can condition low-level differential signals in diagnostic and medical equipment when the design requires low input bias current and flexible gain. Its 20 pA maximum bias current reduces error from high-source-impedance sensors, while the 106 dB minimum common-mode rejection helps reject coupled common-mode voltage. The adjustable gain range supports signal levels from millivolts to larger sensor outputs. Designers must independently validate patient-contact isolation, applicable medical standards, noise margins, and safety requirements rather than treating amplifier performance alone as system compliance.
Recommended
Industrial Process Measurement
The INA111AP is useful in industrial process-measurement systems that combine a low-level sensor with a 12 V to 36 V supply environment. The 106 dB minimum common-mode rejection helps reject process-coupled noise, and the 2 MHz bandwidth at gain 10 can accommodate sensors with dynamic content. Select a gain from 1 to over 1,000 V/V according to sensor sensitivity, then evaluate offset and drift over the intended temperature range. The through-hole package also supports repairable and mixed-technology industrial controller boards.
Recommended
Rapid Data-Acquisition Front End
The INA111AP supports rapid data acquisition when the selected gain preserves useful settling performance. The device settles to 0.01% in 4 µs at gain 100 and maintains 2 MHz bandwidth at gain 10, making it more responsive than a general-purpose precision amplifier in suitable signal chains. Place the external gain resistor close to the RG pins and use short, symmetric input routing to minimize conversion-dependent errors. Confirm the complete acquisition timing from the source through amplifier and converter rather than relying on amplifier bandwidth alone.
Recommended
Recommended Products Summary
Engineering reference data for INA111AP — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product |
|---|---|
| Package | 8-pin plastic DIP |
| Brand | Texas Instruments |
| Product Type | High-speed FET-input instrumentation amplifier |
| Number of Circuits | 1 circuit |
| Architecture | Current-feedback |
| Gain Range | 1 to over 1,000 V/V |
| Bandwidth at Gain 10 | 2 MHz |
| Settling Time | 4 µs to 0.01% at gain 100 |
| Input Bias Current | 20 pA maximum |
| Input Offset Voltage | 500 µV maximum |
| Common-Mode Rejection | 106 dB minimum |
| Supply Voltage Range | 12 V to 36 V |
Key Differentiators
- Through-hole package supports prototype and mixed-technology assembly (vs INA111AU)
- Single-resistor gain programming supports flexible measurement ranges (vs INA111BU)
- High-speed current-feedback performance for precision signal chains (vs NE5534ANG)
Design Notes
Connect the gain-setting resistor directly between the two RG pins and keep the associated loop physically small. Current feedback circuits can respond quickly, so long RG traces and nearby switching paths may introduce parasitic effects. Route the two inputs symmetrically where practical, maintain a continuous ground reference, and avoid placing test pads or connectors that create unnecessary capacitance on high-impedance input nodes.
Use separate high-frequency bypass and bulk-decoupling capacitors near the positive and negative supply pins. The INA111AP operates across a 12 V to 36 V range, and supply-impedance interactions can affect bandwidth and settling even when the nominal voltage is correct. Follow the manufacturer datasheet for recommended capacitor values and stability configuration, and verify the circuit across the minimum and maximum supply conditions used in the final system.
Do not assume that the INA111AU or INA111BU can replace the INA111AP without a PCB change. The INA111AP uses an 8-pin through-hole package, while those family options use surface-mount packages. Also account for gain-dependent bandwidth when selecting an operating point: the stated 2 MHz bandwidth applies at gain 10, and a gain of 100 produces a 4 µs settling time to 0.01% under the manufacturer's specified test conditions.
For high-impedance sources, minimize leakage from the PCB, connectors, and nearby conductors. The 20 pA maximum input bias current is a major benefit of the FET-input architecture, but contamination and humidity can still create parallel leakage paths. Use guarding where appropriate, keep sensitive nodes away from supply and return-current edges, and validate the complete source impedance and cable arrangement rather than relying only on the amplifier input specification.
Compliance Information
No specific RoHS, REACH, lead-free, halogen-free, or conflict-minerals status is stated in the cited product information. The amplifier is not presented as an automotive-qualified device.
