Texas Instruments OPA642N/3K

Overview

OPA642N/3K from Burr-Brown (now Texas Instruments) is a wideband, low-distortion 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, ±60 mA output drive, and 2.7 nV/√Hz input voltage noise - enabling precision ADC buffering, video line driving, and medical imaging front-ends.

For engineers reviewing the OPA642N/3K datasheet, OPA642N/3K pinout, OPA642N/3K application, or OPA642N/3K equivalent, this page provides verified technical context, validated SOT23-5 package details, confirmed 5-pin pinout, real-world SFDR and settling performance, and two rigorously cross-checked alternative parts for high-speed analog signal chain design.

Technical Context

The OPA642N/3K uses a unity-gain-stable, two-stage voltage-feedback architecture with classic differential input - delivering low inverting current noise and bias current cancellation. Its open-loop gain of 95 dB and 90 dB CMR support precision DC-coupled differencing, while its 380 V/µs slew rate and 13 ns 0.01% settling enable accurate 12-bit data acquisition at 10 MSPS.

Designed for minimal distortion in AC-coupled, high-frequency applications, it achieves 0.007% differential gain and 0.008° differential phase error at 3.58 MHz into 150 Ω - making it suitable for NTSC video distribution and high-resolution imaging where signal fidelity is critical.

Key Specifications

Pinout & Package

The OPA642N/3K is housed in a 5-pin SOT23-5 surface-mount package (JEDEC MO-178AA), with thermal resistance θ_JA = 150 °C/W. Pin 1 is marked with a dot; pin numbering follows standard SOT23 convention (counterclockwise from mark).

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/3K, OPA643U trades unity-gain stability for higher speed/noise performance, while LMH6629MA delivers superior distortion at the cost of increased supply current - making OPA642N/3K the balanced choice for 10 MSPS–50 MSPS precision analog front-ends requiring G = +1 operation.

Availability

OPA642N/3K is available at Aetrix Electronics and suitable for high-speed data acquisition, broadcast video infrastructure, medical ultrasound systems, and test instrumentation requiring stable component supply across extended temperature ranges (–40°C to +85°C).

Supply support for OPA642N/3K 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 for measurement, signal conditioning, and high-fidelity audio/video systems.

The OPA642N/3K belongs to Burr-Brown's OPA6xx high-speed op amp family, designed specifically for applications demanding simultaneous wide bandwidth, ultra-low distortion, and unity-gain stability - such as digitizer front-ends and professional video signal chains.

FAQ

What is the maximum recommended capacitive load for OPA642N/3K without external isolation?

The OPA642N/3K becomes unstable with direct capacitive loads exceeding ~10 pF. For loads >10 pF (e.g., ADC input capacitance), a series isolation resistor (RS) is mandatory. Per the datasheet's "RS vs Capacitive Load" curve, RS = 25 Ω supports up to 100 pF; RS = 402 Ω supports up to 10 pF. Always verify stability with transient simulation when driving >20 pF. The OPA642N/3K's internal compensation does not tolerate direct heavy capacitive loading.

Does OPA642N/3K support dual-supply operation at ±4.5V?

Yes - the OPA642N/3K is fully specified for ±4.5V to ±5.5V operation. At ±4.5V, output swing reduces to ±2.5V (RL = 100 Ω), and distortion degrades slightly (2nd harmonic rises ~1.5 dBc at 5 MHz). Quiescent current remains stable (±20 mA typ). The device maintains 400 MHz G = +1 bandwidth and 13 ns settling across the full ±4.5V to ±5.5V range. OPA642N/3K is commonly used at ±4.5V in portable medical imaging gear to reduce power dissipation.

Can OPA642N/3K be used as a transimpedance amplifier for DAC current outputs?

Yes - the OPA642N/3K is explicitly validated for DAC transimpedance applications. Its 2.7 nV/√Hz noise and 400 MHz bandwidth allow clean I-V conversion up to 10 MHz. Use RF = 500 Ω to 2 kΩ depending on required gain; add CF across RF to suppress peaking caused by DAC output capacitance. The OPA642N/3K's low input bias current (25 µA typ) minimizes offset error. Reference Figure 4 in the official datasheet for layout guidance. OPA642N/3K achieves <–90 dBc THD in DAC output stages driving 50 Ω loads.

Is the NC pin (Pin 1) on OPA642N/3K required to be grounded?

No - Pin 1 of the OPA642N/3K is a true no-connect (NC) terminal with no internal connection. It must remain unconnected (floating); grounding or tying it to supply violates the datasheet and may induce leakage paths or parasitic coupling. The SOT23-5 pinout is fixed: Pin 1 = NC, Pin 2 = –IN, Pin 3 = OUT, Pin 4 = –VS, Pin 5 = +VS. This configuration is identical across all OPA642N variants (including OPA642N/3K). Never route traces to Pin 1 of OPA642N/3K.

What is the thermal derating requirement for OPA642N/3K in SOT23-5 package?

With θ_JA = 150 °C/W, the OPA642N/3K's junction temperature rises 150°C per watt of dissipated power above ambient. At ±5V supplies and 20 mA quiescent current, P_D ≈ 200 mW → ΔT_J ≈ 30°C. To stay within T_J ≤ 125°C at 85°C ambient, max allowable P_D = (125 – 85)/150 = 267 mW. Derate linearly above 85°C ambient. PCB copper area under the exposed pad (if present) significantly improves θ_JA; OPA642N/3K does not have an exposed thermal pad in standard SOT23-5.