The design and the results on the performance of an integrated version of the pulse generator of the liquid argon calibration system are presented. The pulse generator consists of a differential amplifier with automatic offset compensation, a current mirror and a switching logic. These components are integrated on an ASIC chip in CMOS technology. The chip has been tested in the laboratory and during testbeam measurements of the hadronic endcap calorimeter. In addition, the radiation hardness has been investigated under neutron irradiation at a nuclear power station