The basic functionality of all types of detectors is: X-Rays reaching the sensitive area of the detector are converted to electrical charge.
The amount of charge is measured. It is proportional to the dose.
All DDAs as Flat Panel Detectors are build in a matrix structure with a switch (mainly a TFT transistor) associated to each pixel:


A LDA ( Line Diode Array) has the same structure but there is only a single line instead of a matrix.

Three different technologies for DDAs are known:
intrinsic Method („direct Method“) - very inefficient, no products within NDT
direct Method with photoconductor (silicon, amourphous Selen or CdTe ) - more efficient and able to resolve the energy applied
indirect Method (Converting X-Ray to light with scintillator and use „normal“ photodiodes to convert light to electrons) - by far most used DDA technology for NDT