  This paper presents the design of a new monolithic Silicon-On-Insulator pixel
sensor in $200~nm$ SOI CMOS technology. The main application of the proposed
pixel detector is the spectroscopy, but it can also be used for the minimum
ionizing particle (MIP) tracking in particle physics experiments. For this
reason few different versions of pixel cells are developed: a source-follower
based pixel for tracking, a low noise pixel with preamplifier for spectroscopy,
and a self-triggering pixel for time and amplitude measurements. In addition
the design of a Successive Approximation Register Analog-to-Digital Converter
(SAR ADC) is also presented. A 10-bit SAR ADC is developed for spectroscopic
measurements and a lower resolution 6-bit SAR ADC is integrated in the pixel
matrix as a column ADC, for tracking applications.
