Texas Instruments INA118P

Overview

INA118P from Texas Instruments is a precision, low-power instrumentation amplifier designed for high-accuracy signal conditioning in sensor front-ends. It delivers 50 µV maximum offset voltage, 0.5 µV/°C max drift, 110 dB minimum CMR at G = 1000, ±2.25 V to ±18 V dual supply operation, and 350 µA quiescent current - enabling use in battery-powered pressure transmitters and ECG systems.

For engineers reviewing the INA118P datasheet, INA118P pinout, INA118P application, or INA118P equivalent, key selection criteria include its laser-trimmed gain-setting architecture (G = 1 + 50 kΩ/R_G), ±40 V input overvoltage protection, 70 kHz bandwidth at G = 100, and compatibility with both 8-pin PDIP and SOIC packages across –40°C to +85°C.

Technical Context

The INA118P uses a three-op-amp topology with JFET-input stages for low bias current (5 nA max) and integrated overvoltage protection limiting input current to ~6 mA. Its current-feedback architecture maintains bandwidth across gain settings - 800 kHz at G = 1, 70 kHz at G = 100 - while preserving DC accuracy via laser-trimmed 50 kΩ internal resistors.

Operation requires only one external resistor (RG) between pins 1 and 8 to set gain from 1 to 10,000. The reference (Ref) pin enables output level shifting, and input common-mode range extends from (V–) + 2 V to (V+) – 2 V at 25°C, supporting single-supply configurations down to 4.5 V total supply.

Key Specifications

Pinout & Package

INA118P is available in 8-pin plastic DIP (PDIP) package, body size 6.35 mm × 9.81 mm, with through-hole mounting and industry-standard lead spacing.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar instrumentation amplifier applications.

Compared with INA118P, INA818 offers superior DC specs for high-precision metrology, while INA828 provides higher bandwidth for dynamic sensing - both retain identical gain configuration and package compatibility, enabling drop-in upgrades where performance margins allow.

Availability

INA118P is available at Aetrix Electronics and suitable for pressure transmitters, ECG monitors, and weigh scale systems requiring stable component supply across extended production lifecycles.

Supply support for INA118P 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

Texas Instruments is a global semiconductor company specializing in analog and embedded processing technologies, with leadership in precision signal chain solutions.

The INA118P belongs to TI's precision instrumentation amplifier product line, engineered for high-accuracy sensor signal conditioning in industrial, medical, and test equipment where low drift, high CMR, and robust input protection are critical.

FAQ

What is the maximum gain achievable with INA118P and how is it set?

The INA118P supports gains from 1 to 10,000, set by a single external resistor RG connected between pins 1 and 8 using the equation G = 1 + 50 kΩ/R_G. For G = 10,000, RG = 5.001 Ω (4.99 Ω standard value). The internal 50 kΩ resistor network is laser-trimmed for accuracy, and RG stability directly impacts gain drift - metal-film resistors with ≤50 ppm/°C TC are recommended for high-precision applications. INA118P achieves this wide gain range while maintaining 70 kHz bandwidth at G = 100.

Does INA118P support single-supply operation and what are the limitations?

Yes, INA118P operates from a single 4.5-V supply (V+ = 4.5 V, V– = 0 V), with output swing from 60 mV to 2 V and input common-mode range limited to 0.2 V to 4.3 V. However, full performance - including 110 dB CMR and 70 kHz bandwidth - requires dual supplies. Single-supply use necessitates careful Ref pin biasing and degrades linear input range; Figure 7-5 and Figure 7-6 in the INA118P datasheet detail output vs. input voltage boundaries under these conditions.

How does the input overvoltage protection in INA118P work and what fault conditions does it cover?

INA118P uses JFET-based input protection that limits input current to ~6 mA during overvoltage events, allowing safe operation with inputs up to ±40 V - even if power supplies are disconnected. This protects against transient surges, wiring errors, and defibrillation pulses in medical use. The protection is bidirectional and independent per input, so –40 V on V– IN and +40 V on V+ IN simultaneously causes no damage. Unlike resistor-based protection, this architecture adds negligible series resistance (<100 Ω), preserving noise performance and gain accuracy in normal operation.

What is the temperature range specification for INA118P and how do key parameters vary across it?

INA118P is specified for operation from –40°C to +85°C ambient temperature. Over this range, offset voltage drift is ≤0.5 µV/°C, bias current remains ≤5 nA, and gain error stays within ±1% at G = 1000. The 50-kΩ internal resistor drift contributes ≤100 ppm/°C to gain drift, and quiescent current varies from 350 µA to 450 µA. All electrical characteristics in Section 7.5 of the INA118P datasheet include test data across this full temperature range, ensuring guaranteed performance without derating.

Can INA118P replace older instrumentation amplifiers like AD620 or LT1167, and what design changes are needed?

INA118P is not a direct pin-compatible replacement for AD620 or LT1167 due to different pinouts and gain equations (AD620: G = 1 + 49.4 kΩ/R_G; LT1167: G = 1 + 49.9 kΩ/R_G). While all three are 8-pin instrumentation amplifiers, INA118P places RG on pins 1/8 (vs. pins 1/8 for AD620 but pins 2/3 for LT1167), and its Ref pin (pin 5) requires low-impedance grounding to maintain CMR. Layout revision and gain resistor recalculation are required; however, INA118P's ±40 V input protection and lower quiescent current (350 µA vs. 1.3 mA for AD620) offer system-level advantages in rugged, low-power designs.