Texas Instruments OPA858IDSGT

Overview

OPA858IDSGT from Texas Instruments is a decompensated, 5.5GHz gain-bandwidth product FET-input operational amplifier optimized for transimpedance amplifier (TIA) configurations in optical time-of-flight systems. It delivers 2000V/µs slew rate, 2.5nV/√Hz input voltage noise, and stable operation at ≥7V/V gain in an 8-pin WSON package. It enables high-bandwidth photodiode signal conditioning in LIDAR receivers.

For engineers reviewing the OPA858IDSGT datasheet, OPA858IDSGT pinout, OPA858IDSGT application, or OPA858IDSGT equivalent, key selection criteria include closed-loop bandwidth vs photodiode capacitance, power-down timing (13ns turn-on), feedback pin layout for low-parasitic TIA design, and compatibility with time-to-digital converters like TDC7201.

Technical Context

The OPA858IDSGT uses a voltage-feedback architecture with CMOS inputs, enabling ultra-low 10pA bias current and 0.8pF total input capacitance-critical for maintaining phase margin in high-gain, high-capacitance photodiode interfaces. Its decompensated design requires minimum gain of 7V/V for stability, supported by internal compensation tailored to TIA topologies.

It integrates a dedicated FB pin (Pin 1) directly connected to the output, allowing compact feedback routing adjacent to IN– (Pin 3), while NC (Pin 2) provides physical isolation to suppress parasitic coupling. The thermal pad must be connected to VS– for optimal thermal performance in continuous high-speed operation.

Key Specifications

Pinout & Package

OPA858IDSGT is housed in an 8-pin WSON (DSG) package measuring 2.00mm × 2.00mm with an exposed thermal pad. The thermal pad must be soldered to VS– for effective heat dissipation during sustained high-output-swing operation.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar transimpedance amplifier applications.

Compared with OPA858IDSGT, OPA855IDSGT trades ultra-low bias current for lower voltage noise and higher bandwidth, while LMH6629MF/NOPB offers lower noise but reduced layout flexibility and narrower usable capacitance range in photodiode interfaces.

Availability

OPA858IDSGT is available at Aetrix Electronics and suitable for optical time domain reflectometry (OTDR), solid-state scanning LIDAR, and laser distance measurement requiring stable component supply across automotive, industrial, and aerospace production programs.

Supply support for OPA858IDSGT 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 company specializing in analog and embedded processing technologies, with leadership in high-speed amplifiers, data converters, and precision signal chain solutions.

The OPA858IDSGT belongs to TI's ultra-wideband precision op amp product line, engineered specifically for optical sensing front ends where simultaneous low noise, high speed, and photodiode interface stability are mandatory.

FAQ

What is the minimum stable gain for OPA858IDSGT, and why is it specified?

The OPA858IDSGT is decompensated and requires a minimum closed-loop gain of 7V/V for stability. This is due to its internal compensation optimized for high-speed transimpedance applications-reducing dominant-pole capacitance to achieve 5.5GHz GBWP. Operating below this gain risks oscillation, especially with capacitive photodiode loads. The datasheet confirms stability only at G ≥ 7V/V across temperature and supply variations.

How does the FB pin on OPA858IDSGT improve TIA performance compared to standard op amps?

The FB pin (Pin 1) on OPA858IDSGT is internally connected to the output, enabling direct, short-trace feedback resistor placement between FB and IN– (Pin 3). Combined with the intervening NC pin (Pin 2), this layout minimizes parasitic inductance and capacitance at the critical inverting node-suppressing peaking and improving phase margin in high-gain, high-capacitance photodiode interfaces where standard op amps often become unstable.

Can OPA858IDSGT operate from a single 3.3V supply, and what are the input/output voltage limitations?

Yes, OPA858IDSGT operates from a single 3.3V supply (VS+ = 3.3V, VS– = 0V). Input common-mode range extends from VS– to 1.9V (1.4V below VS+), and output swing reaches 2.4V_PP (VOH = 2.4V, VOL = 1.15V) into 200Ω. For optimal TIA linearity, bias IN+ to ~1.65V (midsupply) and ensure photodiode cathode/anode connections respect the input voltage limits per the absolute maximum ratings table.

What is the role of the thermal pad on the OPA858IDSGT WSON package, and how must it be connected?

The exposed thermal pad on the OPA858IDSGT DSG package serves as the primary heat dissipation path. It must be soldered to a PCB copper pour connected to VS– (Pin 5). This connection establishes the thermal reference, improves power handling during sustained 20.5mA operation, and ensures reliable ESD current shunting through the internal protection diodes-failure to connect the pad risks thermal runaway and degraded AC performance.

How does OPA858IDSGT support power-gating in battery-powered LIDAR systems?

OPA858IDSGT features a dedicated PD (power-down) pin (Pin 8) that disables the amplifier core when pulled low (<0.65V). In power-down mode, quiescent current drops to 70–140µA, and turn-off delay is 120ns. This allows precise gating synchronized with laser pulses-enabling burst-mode operation in drone vision or portable 3D scanners to extend battery life without sacrificing timing accuracy.