Texas Instruments OPA657N/250

Overview

OPA657N/250 from Texas Instruments is a 1.6-GHz gain-bandwidth, low-noise, FET-input voltage-feedback operational amplifier in a 5-pin SOT-23 package. It delivers 275 MHz bandwidth at G = +10, 700 V/µs slew rate, and 4.8 nV/√Hz input voltage noise - optimized for wideband photodiode transimpedance amplification, ADC front-end driving, and optical time-domain reflectometry (OTDR) signal conditioning.

For engineers reviewing the OPA657N/250 datasheet, OPA657N/250 pinout, OPA657N/250 application, or OPA657N/250 equivalent, key selection criteria include its decompensated stability (minimum stable gain +7), ±2 pA input bias current, –40°C to +85°C operating range, and compatibility with split-supply (±4 V to ±6 V) or single-supply (8 V to 12 V) configurations.

Technical Context

The OPA657N/250 uses a high-speed complementary bipolar process with a low-noise JFET input stage, enabling exceptional dynamic range in high-impedance, broadband signal chains. Its decompensated architecture prioritizes gain-bandwidth and voltage noise performance over unity-gain stability - requiring minimum closed-loop gain of +7 for stable operation.

It supports both split-supply (±4 V to ±6 V) and single-supply (8 V to 12 V) operation, with rail-to-rail output swing capability (±3.3 V into 100 Ω) and fast overdrive recovery. Input common-mode range extends to ±3.5 V, and output can source/sink ±70 mA, enabling direct drive of 50 Ω test equipment loads without external buffers.

Key Specifications

Pinout & Package

OPA657N/250 is housed in a 5-pin SOT-23 (DBV) package measuring 2.90 mm × 1.60 mm, optimized for high-frequency layout with minimal parasitic capacitance and thermal resistance (R_θJA = 150 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA657N/250, OPA656DR trades 70% bandwidth for guaranteed unity-gain stability and lower DC error, while LMH6629MF/NOPB delivers 2.5× higher GBW and lower noise but demands higher supply voltage and lacks JFET input's ultra-low bias current - making OPA657N/250 the optimal balance for photodiode and ADC front ends at ±5 V.

Availability

OPA657N/250 is available at Aetrix Electronics and suitable for wideband photodiode amplification, optical time-domain reflectometry (OTDR), and high-speed ADC input conditioning requiring stable component supply, consistent parametric performance, and long-term industrial availability.

Supply support for OPA657N/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

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in high-performance op-amps and precision signal-chain solutions.

The OPA657N/250 belongs to TI's high-speed, low-noise FET-input op-amp product line, engineered specifically for optical sensing, test instrumentation, and high-fidelity data acquisition where bandwidth, noise, and input impedance are co-critical.

FAQ

What is the minimum stable gain for OPA657N/250?

The OPA657N/250 is decompensated and requires a minimum closed-loop gain of +7 V/V for stable operation. Attempting unity-gain or G = +2 configurations will result in peaking, oscillation, or degraded phase margin. For lower gains, TI recommends the unity-gain stable OPA656 or OPA659 as alternatives. This gain constraint is inherent to its 1.6-GHz gain-bandwidth optimization and is verified across temperature and supply conditions in the official SBOS197F datasheet.

Does OPA657N/250 support single-supply operation?

Yes, OPA657N/250 supports single-supply operation from 8 V to 12 V, provided input and output common-mode voltages remain within the specified linear range (e.g., VIN between –3.3 V and +3.5 V relative to negative rail). No internal changes are needed - performance metrics including bandwidth, slew rate, and noise remain identical to ±5 V operation. Proper input biasing and output DC level shifting are required, as detailed in Section 8.3.2 of the SBOS197F datasheet.

What is the input bias current specification for OPA657N/250 at 85°C?

At TJ = –40°C to +85°C, the input bias current for OPA657N/250 is specified as ±5000 pA (±5 nA) maximum. At room temperature (25°C), it is ±2 pA typical. This temperature-dependent increase reflects JFET gate leakage behavior and must be accounted for in high-gain transimpedance designs where bias current contributes directly to output offset. The high-grade variant (OPA657UB) improves this to ±1250 pA max over temperature.

Can OPA657N/250 drive a 50 Ω load directly?

Yes, OPA657N/250 can drive a 50 Ω load directly, delivering ±70 mA output current and maintaining 275 MHz small-signal bandwidth when configured per TI's recommended test circuit (Figure 29). However, for optimal matching and measurement accuracy, a 50 Ω series resistor is placed at the output pin to isolate the amplifier from cable reflections - a practice confirmed in the SBOS197F datasheet's AC performance characterization setup.

What package type is used for OPA657N/250?

OPA657N/250 uses the 5-pin SOT-23 (DBV) package, with nominal body dimensions of 2.90 mm × 1.60 mm. This surface-mount package features exposed pad thermal enhancement and is distinct from the 8-pin SOIC (D) variant (OPA657U). Pinout is fully compatible across packages, but thermal resistance differs: R_θJA = 150 °C/W for DBV versus 125 °C/W for D, impacting power dissipation limits in continuous high-output applications.