Texas Instruments OPA404KU

Overview

OPA404KU from Texas Instruments (formerly Burr-Brown) is a quad high-speed precision dielectrically isolated FET (Difet®) operational amplifier in 16-pin SOIC package, delivering 6.4MHz gain bandwidth, 35V/µs slew rate, ±750µV max input offset voltage, ±4pA max input bias current, and 1.5µs settling time to 0.01% - used in precision instrumentation front-ends requiring low drift and ultra-low input current.

For engineers reviewing the OPA404KU datasheet, OPA404KU pinout, OPA404KU application, or OPA404KU equivalent, this page provides verified specifications, validated SOIC-16 pin mapping, real-world use cases in medical and ultrasound signal conditioning, and two confirmed alternative quad FET op amps with documented parameter trade-offs.

Technical Context

The OPA404KU employs a cascode input stage architecture that decouples input FET gate voltage from common-mode variations, enabling stable ±4pA bias current across ±10.5V common-mode range. Its laser-trimmed thin-film resistors achieve ±750µV max offset and ±5µV/°C drift over 0°C to +70°C.

Designed for unity-gain stability, it delivers 6.4MHz GBW at ±15V supply with 1000pF capacitive load tolerance and supports rail-to-rail output swing of ±11.5V into 2kΩ - critical for wide-dynamic-range photodiode and detector array amplification.

Key Specifications

Pinout & Package

OPA404KU is housed in a 16-pin plastic SOIC (DW) package with 1.27mm pitch, 10.3mm × 7.5mm body, and moisture sensitivity level 3 (260°C reflow). Pin 1 is located at the top-left corner with notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quad FET operational amplifier applications.

Compared with TL084CDR and AD824ARZ, the OPA404KU uniquely combines 6.4MHz bandwidth, ±4pA bias current, and laser-trimmed offset in a single quad SOIC - making it irreplaceable in high-fidelity sonar front-ends and low-leakage detector array interfaces where both speed and DC accuracy are mandatory.

Availability

OPA404KU is available at Aetrix Electronics and suitable for precision instrumentation, medical equipment, and ultrasonic transducer signal conditioning requiring stable component supply across extended production lifecycles.

Supply support for OPA404KU 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 acquired Burr-Brown in 2000 and maintains its precision analog portfolio, renowned for high-performance op amps, data converters, and interface ICs serving industrial, medical, and test equipment markets.

The OPA404KU belongs to the Difet® precision op amp family, engineered specifically for applications demanding ultra-low input bias current, low offset drift, and high-speed performance in DC-coupled sensor signal chains.

FAQ

What is the maximum operating temperature range for the OPA404KU?

The OPA404KU is specified for operation from 0°C to +70°C ambient temperature. This commercial-grade range is validated per TI's ordering information and matches the "KU" suffix designation. Operation outside this range may cause parametric shift in offset voltage, bias current, or gain bandwidth - the OPA404KU does not support extended industrial (–40°C to +85°C) or military (–55°C to +125°C) temperature grades.

Does the OPA404KU require external compensation for unity-gain stability?

No, the OPA404KU is internally compensated for unity-gain stability. It achieves stable operation with closed-loop gains ≥1 without external capacitors or resistors. This is confirmed in the "DESCRIPTION" section of the datasheet stating "The OPA404 is unity-gain stable," and verified by its 1000pF capacitive load tolerance in the "SPECIFICATIONS" table - enabling direct use as a buffer in ADC driver and line-receiver applications.

How does the OPA404KU's Difet® architecture differ from standard BIFET op amps?

The OPA404KU uses dielectrically isolated FET (Difet®) technology, which places an insulating oxide layer beneath the input FETs to eliminate substrate leakage paths. Unlike BIFET amplifiers, this architecture prevents input destruction during –VCC loss and maintains ±4pA bias current across full common-mode range - as demonstrated in Figure 4 showing flat bias current vs. common-mode voltage, unlike the rising curves of LF155 or AD547.

Can the OPA404KU drive heavy capacitive loads such as LCD panels or long cables?

Yes, the OPA404KU is characterized for stable operation with up to 1000pF capacitive load at unity gain, as stated in the "FREQUENCY RESPONSE" section. This capability allows direct driving of LCD column lines or 1–2 meter coaxial cables without series isolation resistors - critical for maintaining signal integrity in ultrasound imaging and industrial HMI displays where added components would degrade bandwidth or introduce noise.

What is the purpose of the NC pins (8 and 16) on the OPA404KU SOIC package?

Pins 8 and 16 on the OPA404KU are designated No Connect (NC) per TI's DW-16 package drawing and the "PIN CONFIGURATION" diagram. These pins are internally unconnected silicon pads with no electrical function. They must remain unconnected on the PCB - routing traces or applying solder to them risks internal shorting or contamination-induced leakage, which could compromise the ±4pA input bias current specification.