onsemi OPB703

Overview

OPB703 from Fairchild Semiconductor is a reflective object sensor comprising an infrared LED emitter and a phototransistor detector in a single 4-pin DIP package, with typical sensing distance of 0.15 inch (3.8 mm), 30 mA LED forward current rating, and collector-emitter saturation voltage of 0.4 V at I_C = 2 mA. It is used for non-contact position detection in printer paper-path sensing and mechanical end-stop verification.

For engineers reviewing the OPB703 datasheet, pinout, applications, or equivalent options, key selection considerations include emitter wavelength (940 nm), detector spectral response match, output saturation behavior under varying reflectance, and ambient light rejection capability in industrial enclosures.

Technical Context

The OPB703 integrates a GaAs infrared LED and a silicon NPN phototransistor in a molded black plastic housing with optical isolation between emitter and detector. Its internal geometry fixes the optical path angle to optimize reflection capture from flat, diffuse surfaces within 0–3.8 mm range.

Operation requires separate biasing: the LED is driven with pulsed or DC current up to 60 mA (peak), while the phototransistor collector is pulled up to V_CC (≤ 30 V) with load resistor selected to achieve desired switching threshold and response speed (typ. 15 µs rise, 20 µs fall).

Key Specifications

Pinout & Package

OPB703 uses a 4-pin dual-in-line (DIP) through-hole package with 0.3-inch row spacing and standard 0.1-inch pin pitch. Pins are arranged as two parallel rows of two pins each, with emitter anode/cathode on one side and phototransistor emitter/collector on the other.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar reflective object sensing applications.

Compared with TCRT5000 and EE-SX1041, the OPB703 offers the lowest component count for basic on/off detection, maintains strict 0.3-inch DIP compatibility, and delivers proven robustness in cost-sensitive electromechanical systems where 3.8 mm range and 20 µs timing meet design requirements.

Availability

OPB703 is available at Aetrix Electronics and suitable for printer paper-path sensing, industrial limit switch replacement, encoder index detection, and vending machine coin validation requiring stable component supply across long-lifecycle production programs.

Supply support for OPB703 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, signal conditioning, and optoelectronic components before its acquisition by ON Semiconductor in 2016.

The OPB703 belongs to Fairchild's legacy reflective sensor family designed for reliable, low-cost, non-contact object detection in electromechanical systems where size, simplicity, and ambient light immunity are primary constraints.

FAQ

What is the operating temperature range for the OPB703?

The OPB703 is rated for operation from –25°C to +85°C ambient temperature. This range supports deployment in office printers, factory-floor automation equipment, and indoor vending machines. Derating of LED forward current may be required above 70°C to maintain phototransistor output stability. The OPB703 datasheet specifies performance parameters only within this validated thermal envelope.

Can the OPB703 detect transparent or glossy objects reliably?

No - the OPB703 relies on diffuse reflection from matte, opaque surfaces. Transparent materials (e.g., glass, clear plastic) transmit most 940 nm IR light, while glossy surfaces cause specular reflection away from the phototransistor. Testing with actual target materials is required. The OPB703 is not recommended for such use cases; alternative sensors with retroreflective or through-beam topology should be considered instead of the OPB703.

What is the recommended LED current-limiting resistor value for OPB703 at 5 V supply?

With a typical LED forward voltage of 1.2 V at 30 mA, a 120 Ω resistor is recommended for 5 V operation (R = (5 V – 1.2 V) / 0.03 A ≈ 127 Ω; standard 120 Ω provides 31.7 mA). This ensures nominal optical output while staying within absolute maximum ratings. The OPB703 must not be operated above 60 mA peak, even with short pulses.

Does the OPB703 require external shielding from ambient light?

No - the OPB703's black epoxy housing and internal optical barrier provide effective ambient light rejection up to 10 klux of fluorescent or incandescent illumination. No additional shielding is needed in typical indoor industrial environments. However, direct exposure to sunlight or high-intensity IR sources (e.g., halogen lamps) may saturate the phototransistor and should be avoided in system-level mechanical design for the OPB703.

Is the OPB703 RoHS compliant?

Yes - the OPB703 manufactured after 2006 complies with EU RoHS Directive 2011/65/EU, with lead content below 1000 ppm and no restricted substances above threshold limits. Legacy batches may carry different compliance markings; Aetrix Electronics supplies only RoHS-compliant OPB703 units with full traceability documentation available upon request.