  The Particle And Astrophysical Xenon Experiment III (PandaX-III) is an
experiment to search for the Neutrinoless Double Beta Decay (NLDBD) using 200
kg radio-pure high-pressure gaseous xenon TPC with Micromegas detectors at both
ends and cathode in the middle. A small-scale TPC equipped with 7 Microbulk
Micromegas detectors is developed as the prototype detector. 128 channels are
readout following an X-Y design with strips of 3 mm pitch (64 channels each
direction) from one Micromegas module. Highly integrated front-end electronics
composed of 4 front-end cards with 1024 readout channels is designed to readout
the charge of Micromegas anode signals, digitize the waveform after shaping and
send compressed data to the DCM board. The cornerstone of the front-end
electronics is a 64-channel application specific integrated circuit which is
based on a switched capacitor array. The integral nonlinearity of the front-end
electronics is less than 1% with 1 pC. The noise (RMS) of each readout channel
is less than 0.9 fC with 1 microsecond peaking time and 1 pC range. Using the
radioactive sources 56 Fe and 137 Cs, joint-tests of front-end electronics with
the prototype TPC were carried out and the hit map of 7 Micromegas has been
reconstructed.
