A Simple method to measure and improve linearity of flash ADCs used in integrated VME ADC modules

Furutaka, Kazuyoshi  ; Kimura, Atsushi   ; Koizumi, Mitsuo ; Toh, Yosuke   ; Kin, Tadahiro; Nakamura, Shoji  ; Oshima, Masumi

To measure and improve differential linearity of flash ADCs used in integrated VME ADC modules, exponentially falling pulse-tails were digitized and counts of the resultant digital codes were recorded. The obtained histograms were fit to a function to deduce smoothly varying curves which should correspond to that obtained in the case of ideal linearity, and were compared to the fit value to calculate code width for each code. The obtained results show zigzag shaped deviation of about 10 % in magnitude from unity in the whole range and some large spikes which are as large as 100 %. A simple method is proposed to correct the nonlinearity using the ratios in post-processors following the ADCs. In the conference, the results of the correction will be presented.