AXUV20ELG 20-Element Photodiode Array — Specifications & Pin-Out

The AXUV20ELG is a 20-element windowless silicon photodiode array built by Opto Diode, a division of ITW, in Camarillo, California, for electron detection. Twenty individually contacted elements share one substrate in a 22-pin dual-in-line package, so an incident beam is read out channel by channel instead of collapsing into a single lumped current. Opto Diode lists it as a “20 Element Photodiode Array Ideal for Electron Detection” under part number ODD-AXU-033 and sells it direct from Camarillo — for pricing, lead time or current availability, ask Opto Diode.

Datasheet: AXUV20ELG datasheet (PDF), Revision November 26, 2019 — electro-optical and thermal tables, responsivity graphs, the dimensioned package drawing and the full pin-description table. Every specification on this page is taken from that document or from the AXUV product listing; ordering and company details come from Opto Diode directly.

What a 20-element array does that a single diode cannot

A single-element detector reports one quantity: total current. The AXUV20ELG splits that measurement into twenty channels. Each element has its own cathode pin and all of them share a common anode on pins 1 and 12, so every channel can be amplified and digitised separately. Comparing the twenty readings shows where along the array the signal lands and how it is distributed — the basis of position and profile measurement in electron detection, and the reason a segmented array is specified in the first place.

That structure also changes how the front end is designed. Shunt resistance is specified per element (minimum 100 MΩ), which is the figure that matters when sizing a transimpedance amplifier for one channel rather than for the whole device. Twenty channels means twenty amplifier inputs, twenty feedback networks and a readout scheme that keeps crosstalk and gain matching under control across the array.

The AXUV20ELG uses the AXUV process, specified for high-performance measurement of photons, electrons or X-rays from 0.0124 nm to 190 nm, with detection of energies from 100 eV to 50 keV, 100% internal quantum efficiency and windowless construction for enhanced response below 200 nm. The wavelength range and the energy range are two separate specifications of the family; they do not convert into one another. The AXUV photodiode operating principles page explains the physics behind them.

Electro-optical characteristics at 25 °C

Three details are worth reading carefully before this part goes into a design:

• Active area. The datasheet gives the dimension 0.75 mm × 4.1 mm against a typical value of 3 mm², and the AXUV product listing shows the same 3 mm² for the AXUV20ELG. The datasheet does not label that value as per element or as the array total, so confirm the geometry with Opto Diode before committing to an aperture, a mask or a mounting plate.
• Responsivity is a curve, not a number. It is published as graphs rather than a single A/W figure, so read the value for your energy or wavelength off the plots in the datasheet.
• Reverse breakdown voltage is a limit, not a bias recommendation. The 20 V minimum and 25 V typical are measured at 1 µA of reverse current, which is the condition the datasheet uses to define breakdown — an absolute limit, not a bias to operate at. Capacitance and rise time are both specified at V_R = 0 V, that is, at zero reverse bias.

Temperature ratings

The ambient range carries a footnote worth heeding: temperatures exceeding it may create oxide growth on the active area, and over time responsivity to low-energy radiation and to wavelengths below 150 nm will be compromised. The wider −20 °C to 80 °C range applies under nitrogen or vacuum, which is the environment most electron-detection and beamline installations already provide.

Package and pin-out

The AXUV20ELG comes in a 22-pin dual-in-line package with the protective cover plate described above. The dimensioned package drawing is on page 3 of the datasheet, alongside the pin-description table reproduced here.

Read that table carefully, because the numbering is not what a quick glance suggests. As the datasheet’s pin table lists them, the cathodes brought out to package pins are Elements 2 through 21 — twenty channels, with Cathode Element 1 and Cathode Element 22 both marked n/a. The odd-numbered elements come out on pins 2 through 11, the even-numbered elements on pins 13 through 22, and pins 1 and 12 carry the common anode. Element numbers therefore do not map one-to-one onto pin numbers in either direction, so map channel to pin from this table when you lay out a board or wire a feedthrough — and confirm the assignment against the package drawing, or with Opto Diode, before the design is committed.

Where the AXUV20ELG is used

• Electron detection — the application Opto Diode lists for this part, with twenty channels resolving how electron flux is distributed across the array rather than reporting one summed current.
• Synchrotron radiation monitoring — beamline measurement across the AXUV range, where a segmented detector gives a profile across the beam.
• Electron reticle inspection — semiconductor mask and reticle work.

If you are still choosing between families, the AXUV vs SXUV selection guide compares them directly, and how to choose a photodetector covers active area, speed and packaging trade-offs.

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Browse the full AXUV photodiode range.

Frequently Asked Questions

Specifications from the AXUV20ELG datasheet, Revision November 26, 2019. Reviewed and updated July 2026.