  This paper describes the electronics of NEXT-White (NEW) detector PMT plane,
a high pressure xenon TPC with electroluminescent amplification (HPXe-EL)
currently operating at the Laboratorio Subterra\'aneo de Canfranc (LSC) in
Huesca, Spain. In NEXT-White the energy of the event is measured by a plane of
photomultipliers (PMTs) located behind a transparent cathode. The PMTs are
Hamamatsu R11410-10 chosen due to their low radioactivity. The electronics have
been designed and implemented to fulfill strict requirements: an overall energy
resolution below 1% and a radiopurity budget of 20 mBq unit-1 in the chain of
214Bi . All the components and materials have been carefully screened to assure
a low radioactivity level and at the same time meet the required front-end
electronics specifications. In order to reduce low frequency noise effects and
enhance detector safety a grounded cathode connection has been used for the
PMTs. This implies an AC-coupled readout and baseline variations in the PMT
signals. A detailed description of the electronics and a novel approach based
on a digital baseline restoration to obtain a linear response and handle AC
coupling effects is presented. The final PMT channel design has been
characterized with linearity better than 0.4% and noise below 0.4mV .
