Feature: Power management
temperature coefficient, about 20mV per K for the breakdown voltage. Tis figure is up to an order of magnitude lower than in many legacy APDs and, combined with the low dark current and excess-noise performance, it allows operation over a much wider ambient temperature range without complex thermal management. For time-of-flight optics, the APD must
survive and correctly measure signals that range from a handful of photons to very strong reflections. In an automotive LiDAR setup, for example, one moment there could be a reading of a weak return from a distant back tyre, the next could be a powerful flash from a nearby reflective number plate, so the detector must cope with such an extreme dynamic range without damage. Tests on Aura devices show that they keep working even aſter repeated exposure to infrared pulses with intensities of some 40MW/cm². High optical loads can also slow down
recovery from saturation, but this effect can be minimised by carefully matching the APD to its trans-impedance amplifier (TIA), so that the photodiode current is efficiently converted into voltage. Using this approach, a prototype receiver module with Aura running at a gain of 10 recovers from a 500kW/cm² overload in under 1.5µs. When increasing the gain to 100, the overload recovery time for the same optical hit is still only about 2.5µs, so the detector is quickly ready for the next return pulse. Co-designing the APD and TIA also
makes it easier to pinpoint the arrival time of each incoming signal, which in turn improves the precision of the distance measurements. Accurate timing requires the signal response to have a rapid rise time and an equally fast decay time, and the prototype module demonstrated that it can distinguish between pulses arriving just 10ns apart.
Designing new IR systems By bringing together high sensitivity, low noise and carefully tuned behaviour for speed, impulse response, overload recovery and high temperature operation, Aura APDs provide a single device for a wide range of infrared system roles. Tey can be “dropped” into slots in many existing designs, which may be occupied by standard InGaAs APDs – only to see an immediate upliſt in performance without major hardware changes. When designing a new IR system, that
extra sensitivity allows the use of far cheaper solid state lasers yet still hit the target range and accuracy levels, which cuts size, power, bill of materials and overall system complexity. Depending on what the application needs
most, the sensitivity margin can be traded for higher measurement speed, reliable operation at elevated temperatures, or a significant extension in usable range, in some cases by as much as 50%.
www.electronicsworld.co.uk April 2026 19
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