Texas Instruments INA128P

Overview

INA128P from Texas Instruments is a precision, low-power instrumentation amplifier designed for high-accuracy signal conditioning of low-level differential sensor outputs in the presence of large common-mode voltages. It delivers 50 μV max offset voltage, 0.5 μV/°C max drift, 1.3 MHz bandwidth at G = 1, 120 dB min CMRR, and ±40 V input overvoltage protection - enabling robust use in industrial pressure transmitters and medical ECG front-ends.

For engineers reviewing the INA128P datasheet, INA128P pinout, INA128P application, or INA128P equivalent, key selection criteria include gain-setting resistor dependency (G = 1 + 50 kΩ/R_G), PDIP-8 package thermal resistance (R_θJA = 46.1 °C/W), dual-supply operation (±2.25 V to ±18 V), and confirmed performance across –40°C to +85°C.

Technical Context

The INA128P implements a three-op-amp topology with current-feedback input stages, enabling stable 200 kHz bandwidth even at G = 100. Its laser-trimmed thin-film resistors ensure precise gain accuracy and high CMRR (>120 dB at G = 100) without external matching components.

Input overvoltage protection circuitry clamps ±40 V faults directly at the input pins without latch-up or damage, while the REF pin provides output level shifting capability - supporting single-ended output referencing independent of supply rails.

Key Specifications

Pinout & Package

INA128P is supplied in an 8-pin plastic DIP (PDIP) package measuring 9.81 mm × 9.43 mm, with through-hole mounting and industry-standard pin spacing (0.300″ row-to-row).

Key Features

Applications

Equivalent & Alternatives

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

Compared with INA128U and INA828, the INA128P offers superior thermal performance in through-hole layouts and proven field reliability in industrial transmitters, while maintaining identical electrical specifications and pin compatibility within the INA12x family.

Availability

INA128P is available at Aetrix Electronics and suitable for pressure transmitters, temperature transmitters, and weigh scale systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for INA128P 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 INA12x product line was engineered for high-accuracy, low-power instrumentation in industrial sensing and medical diagnostics - emphasizing laser-trimmed DC precision, robust input protection, and flexible gain configuration.

FAQ

What is the maximum gain achievable with INA128P?

The INA128P supports gains from 1 to 10,000 using a single external resistor connected between pins 1 and 8. At G = 10,000, the required RG is 5 Ω (±1% tolerance). The device maintains ≥120 dB CMRR and stable operation up to 20 kHz bandwidth at this gain. Performance data for G = 10,000 is validated in the official INA128P datasheet SBOS051G.

Does INA128P require external capacitors for stability?

Yes - a 0.1 μF ceramic capacitor must be placed between V+ (pin 7) and V– (pin 4), close to the INA128P package, to ensure stability under all operating conditions. Additional 10 μF bulk capacitance is recommended on each supply rail. The INA128P remains stable driving capacitive loads up to 1000 pF, but larger loads require isolation resistors per Section 8.5 of the datasheet.

Can INA128P operate from a single 5-V supply?

Yes - the INA128P supports single-supply operation from 4.5 V to 36 V. When using +5 V only, connect V– (pin 4) to ground, V+ (pin 7) to +5 V, and configure REF (pin 5) to mid-rail (e.g., 2.5 V) to maximize output swing. Input common-mode range becomes 2 V to 3 V, and output swings from ~0.15 V to ~4.85 V (CSO: FRE) per datasheet Figure 6-23.

How does the REF pin affect INA128P output?

The REF pin (pin 5) sets the DC offset of the INA128P output: VO = G × (VIN+ − VIN−) + V_REF. Driving REF with a precision voltage (e.g., DAC output or filtered reference) enables level-shifting without additional op-amps. However, impedance at REF must remain <8 Ω to preserve CMRR; higher impedances degrade rejection by up to 40 dB.

Is INA128P pin-compatible with INA129P?

Yes - INA128P and INA129P share identical pinouts, package dimensions, and absolute maximum ratings. The sole functional difference is the gain equation: INA128P uses G = 1 + 50 kΩ/R_G, while INA129P uses G = 1 + 49.4 kΩ/R_G. This allows INA129P to serve as a drop-in replacement for legacy devices requiring 49.4 kΩ-based gain scaling, but INA128P remains standard for new designs.