  The ARGO-YBJ experiment, currently under construction at the Yangbaijing
Laboratory (4300 m a.s.l.), consists of a single layer of about 2000 Resistive
Plate Chambers (RPCs) for a total instrumented area of about 6700 m^2. The
digital read-out, performed by means of pick-up electrodes 6.7 X 62 cm^2
('strips'), allows one to measure the particle number of small size showers. To
extend the size range up to the knee region it is necessary to implement the
charge read-out of the detector chambers. In order to achieve this goal each
RPC has been instrumented with two large size pads of dimensions 140 X 125
cm^2. In this paper the performance of the prototype circuit devoted to the
charge read-out is reported.
