OPA655U - Wideband FET Op Amp, ±5.25 V | Texas Instruments
MPN: OPA655U ✓ ActiveOPA655U Overview
A voltage-feedback operational amplifier is a transistor-based analog circuit that amplifies the voltage difference between its inverting and non-inverting inputs. The voltage-feedback amplifier family belongs to the broader operational-amplifier hierarchy, analog IC hierarchy, and semiconductor hierarchy. Unlike a current-feedback amplifier, a voltage-feedback amplifier uses internal frequency compensation, allowing it to remain stable at unity gain when configured with suitable feedback and source impedances.
The OPA655U provides eight key verified characteristics. It is a wideband amplifier, is stable at a gain of one, uses a FET input, contains one amplifier circuit, accepts a supply specified as ±5.25 V, and is available in an 8-pin SOIC package. The listed temperature grade is industrial, while the package uses a gull-wing surface-mount form. These characteristics make it applicable where a precision input device is required within a modest-size instrumentation circuit.
OPA655U belongs to the wideband, low-noise amplifier class rather than the general-purpose precision op-amp class. Its FET input is the defining input-stage technology reported by the manufacturer data, while unity-gain stability supports direct use as a buffer when the application conditions satisfy the amplifier's operating requirements. The 8-SOIC format provides a conventional surface-mount footprint that is also used by several related high-speed amplifier families.
Typical uses include photodiode and optical-signal conditioning, waveform monitoring, laboratory instrumentation, communications-interface signal paths, precision feedback networks, and high-speed data-acquisition front ends. In these systems, the amplifier can condition a small differential signal before it reaches an ADC, implement active filtering, or drive a subsequent analog stage when the voltage and current limits of the selected feedback network remain within device specifications.
Designers should verify the required supply rails, input common-mode range, output swing, input bias current, noise density, slew rate, gain-bandwidth behavior, and stability conditions directly against the manufacturer datasheet before release. Layout should provide a short, low-impedance feedback path and careful grounding to avoid adding parasitic gain or instability. Component values and timing margins should be derived from the datasheet's tested application circuits rather than inferred solely from the generic amplifier category.
This page consolidates the verified distributor and manufacturer information, separates known OPA655U attributes from parameters that still require datasheet confirmation, and documents the only supported drop-in cross-reference found in the supplied replacement search. It also provides purchasing guidance, application fit, comparison boundaries, and practical design checks that help engineers distinguish a genuine replacement from a merely similar amplifier.
Drop-in alternatives for OPA655U — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
OPA656U
✅ Drop-InContact for price
View Datasheet →OPA655U Maximum Ratings & Electrical Characteristics
| Amplifier Type | Voltage Feedback Amplifier |
| Number of Circuits | 1 circuit |
| Input Stage | FET input |
| Gain Stability | Unity-gain stable |
| Frequency Class | Wideband |
| Supply Voltage | ±5.25 V |
| Package | 8-SOIC |
| Number of Terminals | 8 terminals |
| Terminal Form | Gull wing |
| Package Shape | Rectangular |
| Package Code | SOP |
| Temperature Grade | Industrial |
| Mounting Type | Surface mount |
OPA655U sop Pin Configuration Guide
Pin configuration for OPA655U (sop package). This analog component features input, output, and power supply pins. Refer to the manufacturer datasheet for offset null, compensation, and enable pin configurations. Ideal for signal conditioning and amplifier circuits.
No detailed pinout data available for OPA655U.
Refer to the datasheet for full pin configuration.
Typical Applications
OPA655U is suitable for 6 applications: Photodiode Signal Conditioning, Precision Instrumentation Signal Path, High-Speed Data Acquisition Front End, Active Filtering and Feedback Control, Communications Interface Conditioning, Precision Buffering and Signal Termination.
Photodiode Signal Conditioning
OPA655U fits a wideband photodiode front end because the verified device description identifies a FET-input, unity-gain-stable voltage-feedback amplifier in an 8-SOIC package. It can be evaluated in a transimpedance topology where the photodiode capacitance, feedback resistance, and required signal bandwidth determine stability and gain. The supplied replacement evidence identifies OPA656U as a functional upgrade in high-speed photodiode circuits, supporting the family’s suitability for this role. Before release, verify input bias current, input capacitance, noise density, slew rate, output swing, and the datasheet’s recommended transimpedance feedback network.
Recommended
Precision Instrumentation Signal Path
OPA655U is suitable for a general instrumentation signal path when the circuit needs wideband voltage-feedback amplification rather than a general-purpose op amp. Its verified unity-gain stability allows engineers to evaluate the device as a buffer or as part of an inverting or non-inverting amplifier, subject to the manufacturer’s source-impedance and feedback recommendations. The single-circuit 8-SOIC implementation also supports compact test and measurement boards. Gain-bandwidth, offset, bias current, noise, input-range, and output-swing values must be obtained from the datasheet before setting the system error budget.
Recommended
High-Speed Data Acquisition Front End
OPA655U can serve as the analog gain stage immediately before an ADC when the required signal bandwidth is compatible with its wideband voltage-feedback architecture. The verified unity-gain-stable characteristic supports designs where a one- or higher-gain configuration is needed, while the FET input identifies the device as appropriate for high-impedance source evaluation. The engineer must still establish the maximum signal bandwidth, settling requirements, output swing, ADC drive-capability match, and allowable phase margin from the manufacturer datasheet before finalizing the filter and sampling chain.
Recommended
Active Filtering and Feedback Control
OPA655U is applicable to active-filter and feedback-control circuits because it is a wideband, unity-gain-stable voltage-feedback amplifier with one amplifier circuit per package. The 8-SOIC format provides access to a conventional analog implementation without requiring a high-density mixed-signal package. Component selection depends on the filter topology, closed-loop gain, operating frequency, allowable phase margin, input common-mode range, and output loading. Those detailed limits were not supplied in the verified excerpts, so stability and dynamic-range calculations must use the manufacturer datasheet rather than generic voltage-feedback assumptions.
Recommended
Communications Interface Conditioning
OPA655U can be evaluated for communications-interface signal conditioning where a low-level differential input must be amplified into a useful logic or converter range. Its wideband nature provides the appropriate amplifier category for higher-frequency signals, while the FET input supports testing with high-impedance sources. The implementation still needs to address input-referred noise, offset, common-mode limits, output swing, and the bandwidth required by the communication protocol. The 8-SOIC package and documented same-pinout OPA656U route also facilitate controlled A/B testing without changing the PCB footprint.
Recommended
Precision Buffering and Signal Termination
OPA655U can be evaluated as a unity-gain buffer because the verified data explicitly identifies the device as unity-gain stable. In this role it can isolate a source from the following stage, buffer a sensor or reference network, or provide impedance matching within a test fixture. Unity-gain operation does not eliminate design checks: source impedance, capacitive loading, output current, output swing, and stability at the actual gain must all satisfy the datasheet. The industrial-grade listing and compact 8-SOIC outline make the device a candidate for industrial instrumentation boards where a qualified grade is required.
Recommended
Recommended Products Summary
Engineering reference data for OPA655U — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | OPA656U |
|---|---|---|
| Brand | Texas Instruments | Texas Instruments |
| Package | 8-SOIC | 8-SOIC - same package and pinout |
| Amplifier Type | Voltage Feedback Amplifier | Voltage Feedback Amplifier |
| Number of Circuits | 1 circuit | 1 circuit |
| Input Stage | FET input | FET input |
| Gain Stability | Unity-gain stable | Unity-gain stable |
| Supply Voltage | ±5.25 V | 8 V to 12 V in the supplied replacement listing |
Key Differentiators
- Documented pin-compatible upgrade path without changing the PCB footprint (vs OPA656U)
- Unity-gain-stable wideband operation (vs OPA656U)
- Single-amplifier industrial-grade 8-SOIC implementation (vs OPA656U)
Design Notes
Keep the op-amp input and feedback paths short and route them away from high-current switching nodes. Place the input and feedback components close to the relevant OPA655U pins, maintain a compact ground return around the amplifier, and provide a local bypass capacitor on each supply rail. The verified excerpts confirm an 8-SOIC package but do not specify recommended capacitance or trace geometry, so those values must be taken from the manufacturer datasheet and reference layout.
Treat OPA655U as a voltage-feedback amplifier and evaluate stability with the actual source impedance, load capacitance, feedback resistors, and target gain. Unity-gain stability does not guarantee adequate phase margin in every topology or with every external network. Before production, compare the selected resistor and capacitor values against the manufacturer’s recommended application circuits, and check that photodiode, cable, or probe capacitance does not create ringing or an unexpected response peak.
Do not assume that the OPA656U listing is an unconditional substitute even though the supplied source reports the same 8-SOIC pinout. Its stated supply range differs from the range attributed to OPA655U, and the excerpt explicitly says “most” transimpedance applications. Verify offset, bias current, noise, input range, output swing, slew behavior, and stability for the exact replacement before approving it for production or safety-relevant equipment.
Check signal amplitude, output load, and supply polarity before enabling the circuit because the verified listing identifies OPA655U as a ±5.25 V part. The available excerpts do not include input common-mode limits or output swing, so a nominal ±5.25 V rail does not by itself guarantee linear operation at every amplitude. Derive headroom from the datasheet and include startup, bypassing, and supply sequencing checks in the board-level validation plan.
Compliance Information
The supplied verified excerpts identify the product and industrial temperature grade but do not state RoHS, REACH, lead-free, halogen-free, or conflict-minerals status. AEC-Q100 is marked not_applicable because no automotive qualification claim appears in the supplied data.
