Photodiodes – PIN, Avalanche, and Array Types for Precision Light Detection

Photodiodes are semiconductor devices that convert incident light into electrical current, forming the backbone of optical sensing in industrial automation, medical instrumentation, telecommunications, and consumer electronics. Unlike generic light sensors, photodiodes offer linear response over wide dynamic ranges, fast switching speeds, and excellent long-term stability. Selecting the correct photodiode type — PIN, avalanche (APD), or array configuration — directly determines system sensitivity, bandwidth, and noise performance. At ADD Components, we source photodiodes from industry-leading manufacturers including Vishay, Osram, Broadcom, and ON Semiconductor, supporting procurement teams across Asia with genuine components and competitive lead times.

Sub-Types and Categories

PIN Photodiodes

The PIN photodiode is the most widely used photodetector type, named for its P-type, Intrinsic, and N-type semiconductor layers. The intrinsic (undoped) region between the P and N layers widens the depletion zone, allowing more photons to be absorbed and converted to electron-hole pairs. This structure delivers high quantum efficiency, low capacitance, and fast response times typically in the nanosecond range. PIN photodiodes operate in photovoltaic mode (zero bias) for precision DC measurement or photoconductive mode (reverse bias) for high-speed pulse detection. Common applications include optical communication receivers, barcode scanners, smoke detectors, and spectrophotometers. Key parameters to evaluate are spectral response range (typically 350 nm to 1100 nm for silicon devices), responsivity (A/W), dark current, and rise time. Vishay's BPW34 and BPW21R remain industry-standard PIN photodiodes trusted in millions of designs worldwide. Osram's SFH203 series provides enhanced sensitivity in the near-infrared region, while Broadcom's visible-light photodiodes offer precision-matched spectral characteristics for medical pulse oximetry and ambient light sensing.

Avalanche Photodiodes (APD)

Avalanche photodiodes employ internal gain through impact ionization — a high reverse bias voltage accelerates photo-generated carriers to collide with lattice atoms, liberating additional charge carriers in a cascading avalanche effect. This multiplication mechanism provides gain factors of 50 to 1000, enabling single-photon detection capability in some device classes. APDs are indispensable in long-range LiDAR systems, optical time-domain reflectometry (OTDR), quantum key distribution, and low-light fluorescence detection. The primary trade-off is increased noise from the statistical nature of the multiplication process, quantified by the excess noise factor. Designers must balance gain against noise and must provide stable, temperature-compensated bias voltages — typically 100 V to 500 V for silicon APDs. Vishay, First Sensor (now TE Connectivity), and Hamamatsu dominate the APD market, with devices optimised for wavelengths from UV through to 1700 nm using InGaAs structures for telecom applications. ADD Components can source both silicon and InGaAs APDs for specialised detection applications across industrial and research sectors.

Photodiode Arrays

Photodiode arrays integrate multiple photodetector elements on a single substrate, enabling simultaneous multi-channel or spatially resolved light detection. Linear arrays are used in spectrometry and position sensing, while two-dimensional arrays serve as image sensors in machine vision and medical imaging. Vishay's TEMD5010 and TEMD5110 series combine PIN photodiodes with integrated daylight-blocking filters in compact SMD packages, optimised for 950 nm infrared detection. Quadrant photodiodes split the active area into four independent segments, providing beam-position information for laser alignment, optical tracking, and adaptive optics systems. When selecting photodiode arrays, consider element uniformity, crosstalk between adjacent channels, and the readout circuitry required — many modern devices integrate transimpedance amplifiers directly on the die. Broadcom and Vishay offer array solutions covering visible through near-infrared wavelengths in industry-standard SMD footprints suitable for automated assembly.

Key Selection Parameters

• Spectral response range — Match the photodiode material (Si, InGaAs, Ge) to your target wavelength; silicon covers 350–1100 nm, InGaAs extends to 1700 nm for telecom bands.

• Responsivity — Expressed in A/W, typically 0.5–0.65 A/W for silicon PIN photodiodes at peak wavelength; higher values reduce required amplifier gain.

• Dark current — The leakage current with no illumination; increases with temperature and reverse bias voltage, limiting detectivity in low-light applications.

• Rise/fall time — Determines bandwidth; PIN photodiodes achieve sub-nanosecond speeds, while large-area devices trade speed for sensitivity.

• Active area — Larger areas capture more light but increase capacitance and dark current; match to your optical system's spot size.

• Capacitance — Affects amplifier noise gain and bandwidth; lower capacitance enables higher-speed transimpedance amplifier designs.

• Package type — Through-hole (TO-18, TO-5), SMD (1206, 0805, PLCC), or custom hermetic packages for demanding environments.

Representative Parts We Source

Send Us Your Photodiode Requirements

Whether you need high-volume BPW34 orders for smoke detector production, precision SFH203 devices for optical encoders, or custom photodiode array configurations for spectrometry systems, ADD Components delivers genuine components with full traceability. Our procurement team works directly with Vishay, Osram, Broadcom, and ON Semiconductor authorised channels to secure competitive pricing and reliable delivery schedules throughout Asia.

Send your bill of materials (BOM) to Info@addcomponents.hk for a same-day quotation. Reach our Hong Kong office at +852 5334 3091 or message us on WhatsApp at +852 5334 3091 for urgent component enquiries.

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