Single-Ended-to-Differential Sampling Technique for Sigma Delta ADCs in X-Ray Detectors

A sampling technique for X-ray detectors is presented, which performs a two channel single-ended-to-differential sampling, and buffers the sampled signals serially to the incremental Sigma Delta ADC. This sampling technique maximizes the readout speed of the X-ray detectors, while allowing the ADC to sample the input signal multiple times for reduced thermal noise and higher resolution. The sampler is implemented in 0.25 µm CMOS technology, as a part of a mixed signal processing backend for the pixel signal, consists of buffering, ADC conversion and readout circuits. Measured performance shows a high resolution of >77 dB SNR at 3.3 Kfps, which emphasizes the speed advantage and high linearity of the proposed approach.