Texas Instruments OPA642N/250

Overview

OPA642N/250 from Burr-Brown (now Texas Instruments) is a unity-gain-stable, wideband voltage-feedback operational amplifier optimized for high-dynamic-range signal conditioning. It delivers –95 dBc 2nd harmonic distortion at 5 MHz, 400 MHz gain=+1 bandwidth, 2.7 nV/√Hz input voltage noise, ±60 mA output drive, and 13 ns 0.01% settling time - enabling precision ADC buffering in 10 MSPS digitizers like the ADS804.

For engineers reviewing the OPA642N/250 datasheet, OPA642N/250 pinout, OPA642N/250 application, or OPA642N/250 equivalent, key selection criteria include its low distortion at high frequencies, SOT23-5 package thermal performance (θ_JA = 150°C/W), differential gain/phase error (0.007%/0.008°), and guaranteed ±2.5 V output swing into 100 Ω - critical for video line driving and medical imaging front-ends.

Technical Context

The OPA642N/250 employs a two-stage voltage-feedback architecture with classic differential input, delivering unity-gain stability without external compensation. Its high open-loop gain (95 dB) and common-mode rejection (90 dB) support precision differencing applications, while fast settling (13 ns @ 0.01%) and low noise enable high-fidelity sampling interfaces.

It operates from ±4.5 V to ±5.5 V supplies, draws ±25 mA quiescent current, and maintains stable performance across –40°C to +85°C. The SOT23-5 package uses pins 1 (+VS), 2 (–IN), 3 (OUT), 4 (–VS), and 5 (+IN), with internal power routing optimized for minimal supply impedance and harmonic suppression.

Key Specifications

Pinout & Package

The OPA642N/250 is housed in a 5-pin SOT23-5 package (JEDEC MO-178AA), with θ_JA = 150°C/W and marking code "A42". Shorter bond wires and compact layout yield superior high-frequency distortion performance versus SO-8 or DIP variants.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed, low-distortion op amp applications.

Compared with OPA642N/250, OPA643U trades unity-gain stability for higher speed and lower noise, while LMH6629MA delivers superior distortion at the cost of higher supply current - making OPA642N/250 the balanced choice for general-purpose high-dynamic-range buffering where design flexibility and thermal efficiency are critical.

Availability

OPA642N/250 is available at Aetrix Electronics and suitable for high-resolution imaging systems, professional video infrastructure, medical diagnostic equipment, and automated test instrumentation requiring stable component supply with traceable lot control and long-term lifecycle assurance.

Supply support for OPA642N/250 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 precision analog ICs including high-speed op amps, data converters, and interface solutions for demanding measurement and signal chain applications.

The OPA642N/250 belongs to Burr-Brown's OPA6xx family of wideband, low-distortion operational amplifiers - designed specifically for high-fidelity signal acquisition in digitizers, video systems, and medical imaging front-ends.

FAQ

What is the maximum recommended capacitive load for OPA642N/250 without external isolation?

The OPA642N/250 becomes unstable with >10 pF capacitive load directly on the output pin. For reliable operation, a series isolation resistor (RS) must be used - e.g., 15 Ω for 10 pF, 25 Ω for 22 pF, or 47 Ω for 47 pF - as confirmed by the "RS vs Capacitive Load" curve in the OPA642N/250 datasheet. This prevents peaking and ensures flat frequency response up to 100 MHz.

Does OPA642N/250 require all four supply pins like the SO-8 version?

No - the OPA642N/250 uses only two supply pins (Pin 1 = +VS, Pin 4 = –VS) due to its 5-pin SOT23-5 configuration. Unlike the 8-pin SO-8 or DIP versions, it does not have separate +VS1/+VS2 or –VS1/–VS2 pins. Its compact layout inherently minimizes supply path inductance, contributing to its best-in-class 5 MHz distortion performance.

Can OPA642N/250 drive a 50 Ω transmission line directly?

Yes - the OPA642N/250 is characterized to deliver ±2.75 V into 100 Ω (doubly terminated 50 Ω line), yielding ±1.25 V at the load. With proper 0.1 µF local decoupling on both supplies and a 50 Ω series resistor at the output, it maintains <–90 dBc 2nd harmonic distortion at 5 MHz - making it suitable for RF sampling and high-speed digital I/O line driving.

What is the thermal resistance (θ_JA) of OPA642N/250, and how does it affect PCB layout?

The OPA642N/250 has θ_JA = 150°C/W in the SOT23-5 package. To maintain junction temperature below 125°C at +85°C ambient with ±25 mA quiescent current, PCB layout must include ≥25 mm² of 1-oz copper connected to Pin 1 (+VS) and Pin 4 (–VS) as thermal relief. Avoid narrow traces or isolated pads - thermal vias to inner ground planes significantly improve heat dissipation.

Is OPA642N/250 suitable for driving the ADS804 12-bit, 10 MSPS ADC?

Yes - the OPA642N/250 is explicitly validated for ADS804 interfacing in the datasheet. Its 80 dB SFDR at 5 MHz exceeds the ADS804's 80 dB requirement, and its 13 ns 0.01% settling time provides 2× margin against the 100 ns sampling aperture window. The front-page reference design shows direct AC-coupled connection with 2 V_p-p swing and blocking capacitor level-shifting.