Texas Instruments OPA2381AIDRBT

Overview

OPA2381AIDRBT from Texas Instruments is a dual-channel, precision transimpedance amplifier optimized for photodiode current-to-voltage conversion. It delivers 18MHz gain-bandwidth, 25µV max offset voltage, 0.1µV/°C max drift, 3pA bias current, and >250kHz transimpedance bandwidth in typical configurations-enabling high-fidelity optical signal conditioning in CAT-scan front-ends and photo lab equipment.

For engineers reviewing the OPA2381AIDRBT datasheet, OPA2381AIDRBT pinout, OPA2381AIDRBT application, or OPA2381AIDRBT equivalent, key selection considerations include its DFN-8 package, dual-channel isolation, single-supply operation (2.7V–5.5V), extended 0V output swing capability with pulldown resistor, and verified 5-decade dynamic range (10nA to 1mA) without logarithmic compression.

Technical Context

The OPA2381AIDRBT integrates an auto-zero core with a continuous-time 18MHz signal-path amplifier, correcting offset every 100µs while suppressing 1/f noise and maintaining low 10nV/√Hz broadband voltage noise. Its input stage supports common-mode voltages from V− to (V+) − 1.8V and features ESD-protected diode clamps.

Designed specifically for transimpedance topologies, it enables stable >250kHz bandwidth with photodiode capacitances up to 100pF when paired with appropriate feedback networks (e.g., RF = 1MΩ, CF = 1pF). Fast 200ns positive-rail overload recovery and optional −5V pulldown support precise single-supply zero-referenced output swing.

Key Specifications

Pinout & Package

OPA2381AIDRBT is housed in a 3mm × 3mm DFN-8 package with exposed thermal pad (DRB designation), rated for −40°C to +125°C operation. Pin 1 is NC (no internal connection); pins 2–8 follow standard dual-op-amp functional assignment with shared power rails.

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA2381AIDRBT, OPA2380AIDRBT offers higher bandwidth at the cost of reduced dc precision, while OPA2188AIDR delivers superior drift performance but limits transimpedance bandwidth to ~100kHz - making OPA2381AIDRBT the optimal balance for 250kHz–1MHz optical sensing with 5-decade linearity.

Availability

OPA2381AIDRBT is available at Aetrix Electronics and suitable for CAT-scan front-ends, photodiode monitoring systems, and optical amplifier feedback loops requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for OPA2381AIDRBT 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 precision op amps and signal-chain solutions.

The OPA2381AIDRBT belongs to TI's precision transimpedance amplifier product line, engineered specifically for high-dynamic-range, low-noise optical current measurement in medical, test, and industrial instrumentation.

FAQ

What is the maximum photodiode capacitance supported by OPA2381AIDRBT for >250kHz transimpedance bandwidth?

The OPA2381AIDRBT achieves >250kHz transimpedance bandwidth with photodiode capacitances up to 100pF when used with appropriate feedback compensation (e.g., RF = 1MΩ, CF = 1pF). This is validated in TI's SBOS313B datasheet Figure 6 and confirmed by the 18MHz gain-bandwidth product and low input capacitance (1pF differential + 2.5pF common-mode). Exceeding 100pF requires reducing RF or adding CF to maintain stability, which lowers bandwidth.

Can OPA2381AIDRBT operate from a single 3.3V supply while delivering 0V output swing?

Yes - OPA2381AIDRBT supports true 0V output swing on a single 3.3V supply when a pulldown resistor (e.g., 10kΩ) connects the output to a negative reference such as −1.8V or −5V. The device's output stage is explicitly designed for this configuration, as detailed in the "Achieving Output Swing to Ground" section of the datasheet. Without pulldown, minimum output is ~50mV above V−.

How does the auto-zero architecture of OPA2381AIDRBT affect its noise performance at 10kHz?

The OPA2381AIDRBT's auto-zero correction occurs at 10kHz, but internal filtering suppresses fundamental energy at that frequency; residual artifacts appear >20MHz and are negligible in most applications. Measured input voltage noise remains 10nV/√Hz above 1MHz and 70nV/√Hz at 10kHz - consistent with its precision CMOS process and verified in SBOS313B Figure 7. No external filtering is required for typical optical sensing.

Is OPA2381AIDRBT pin-compatible with OPA2381AIDGKR in MSOP-8 packaging?

No - OPA2381AIDRBT uses DFN-8 (DRB) packaging with NC pins at positions 1, 4, and 5, while OPA2381AIDGKR uses MSOP-8 (DGK) packaging with fully assigned pins including separate In+ B/In− B/Out B. The pinouts differ fundamentally; PCB layout and footprint must be redesigned when switching between these packages. Both share identical electrical specifications and temperature rating.

What is the recommended bypass capacitor for OPA2381AIDRBT's V+ and V− pins?

Texas Instruments specifies a 1µF ceramic or tantalum capacitor from each supply pin (V+ and V−) to ground, placed as close as possible to the DFN-8 package. Electrolytic capacitors are not recommended due to higher ESR and inductance. For high-frequency stability with capacitive loads, a parallel 0.1µF ceramic capacitor may be added, but the 1µF value is mandatory per the "Basic Operation" section of SBOS313B.