Texas Instruments INA116PA

Overview

INA116PA from Burr-Brown (now Texas Instruments) is an ultra-low-input-bias-current FET-input instrumentation amplifier designed for high-impedance sensor signal conditioning. It delivers 3 fA typical input bias current at 25°C, ±2 mV maximum offset voltage, and 84 dB CMRR at G = 10 - enabling precision pH measurement, ion-specific probe interfaces, and leakage current monitoring in laboratory instrumentation.

For engineers reviewing the INA116PA datasheet, INA116PA pinout, INA116PA application, or INA116PA equivalent, this page provides verified technical context, validated pin functions, real-world application mappings, and confirmed alternative options for low-leakage analog front-end design.

Technical Context

The INA116PA uses a 3-op-amp topology with laser-trimmed on-chip 25 kΩ feedback resistors to achieve gain accuracy of ±0.25% at G = 10 and ±0.5% at G = 100. Its Difet® input stage enables sub-femtoampere bias current performance, supported by dedicated guard drive outputs that actively shield input traces and cables.

Input over-voltage protection withstands ±40 V, common-mode range extends to (V+)–2 V and (V–)+2.4 V, and bandwidth ranges from 800 kHz at G = 1 to 7 kHz at G = 1000 - all specified across –40°C to +85°C for industrial-grade reliability.

Key Specifications

Pinout & Package

INA116PA is housed in a 16-pin plastic DIP (PDIP-N) package with through-hole mounting and 0.3-inch body width. Pin spacing follows JEDEC MS-001 standard, with 0.1-inch row pitch and 0.3-inch inter-row distance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-bias-current instrumentation amplifier applications.

Compared with AD8420ARMZ and LMP8272MMX, the INA116PA uniquely delivers femtoampere-level input bias current with integrated guard drivers - making it irreplaceable in pH, ion-selective, and ultra-low-leakage applications where input stage leakage directly determines measurement fidelity.

Availability

INA116PA is available at Aetrix Electronics and suitable for laboratory instrumentation, pH measurement systems, ion-specific probe interfaces, and leakage current monitoring requiring stable component supply across extended product lifecycles.

Supply support for INA116PA includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in high-precision analog ICs including instrumentation amplifiers, data converters, and reference circuits.

The INA116PA belongs to Burr-Brown's Difet® instrumentation amplifier family, engineered specifically for applications demanding femtoampere input bias current and guarded high-impedance signal acquisition - such as analytical chemistry, biomedical sensing, and materials testing.

FAQ

What is the maximum input voltage range supported by the INA116PA?

The INA116PA supports a safe input voltage range of ±40 V, meaning either input (VIN+ or VIN–) can tolerate up to 40 V above or below the negative supply rail without damage. This rating applies regardless of gain setting and is enforced by internal protection diodes. Operation within the common-mode range ((V+)–2 V to (V–)+2.4 V) is required for linear amplification; the ±40 V limit is an absolute maximum survival rating, not a functional operating specification. Always ensure input signals stay within the specified common-mode window for accurate gain behavior.

Does the INA116PA require external offset trimming in typical applications?

No, the INA116PA does not require external offset trimming in most applications because it is laser-trimmed at wafer level to achieve ±2 mV maximum input offset voltage at 25°C and low drift over temperature. The datasheet confirms that "most applications require no external offset adjustment." Only systems demanding sub-100 µV offset accuracy - such as high-resolution weigh scales or calibrated reference monitors - may benefit from optional Ref-terminal trimming using an external op amp circuit, as shown in Figure 2 of the INA116PA datasheet.

How do the Guard+ and Guard– pins function in the INA116PA?

The Guard+ and Guard– pins on the INA116PA provide buffered, low-impedance copies of the VIN+ and VIN– potentials respectively, intended to drive PCB guard traces or cable shields surrounding those inputs. By holding the guard at nearly identical potential to the input, leakage currents across conformal coating, solder mask, or contamination are minimized. Each guard output delivers +2 mA / –50 µA, sufficient for driving coaxial cable shields at DC and low frequencies; for fast signals, an external op amp buffer (e.g., OPA131) is recommended as shown in Figure 6 of the INA116PA datasheet.

Can the INA116PA operate from a single supply?

No, the INA116PA is not designed for single-supply operation. Its internal architecture requires dual symmetric supplies (e.g., ±15 V or ±5 V), with specified operation from ±4.5 V to ±18 V. The common-mode input range is referenced to the supply rails (e.g., (V+)–2 V and (V–)+2.4 V), and the output swing is similarly rail-dependent. Attempting single-supply use will result in saturation, loss of linearity, or undefined behavior. For single-supply instrumentation amplifier needs, consider TI's INA333 or ADI's AD8420 - neither of which match the INA116PA's femtoampere bias performance.

What is the purpose of the Ref pin on the INA116PA?

The Ref pin on the INA116PA sets the output reference voltage - the DC level around which the amplified differential signal swings. It is not a power supply pin but a high-impedance summing node; the output voltage equals G × (VIN+ – VIN–) + V_REF. For most applications, Ref is tied to ground (via low-impedance path) to produce output centered at 0 V. Any resistance >30 Ω in series with Ref degrades CMRR significantly (e.g., to ~72 dB at G = 1), so solid grounding or active buffering is mandatory for precision performance. The INA116PA datasheet emphasizes that Ref must be driven from a low-impedance source to maintain specified CMRR.