Radiation hardness tests on the read out electronics chain of the ALEPH minivertex detector

In ALEPH a double sided microstrip detector has been installed as minivertex detector. Its read out electronics consists of a custom designed VLSI amplifier CAMEX 64, a digital steering chip running the CAMEX and a line driver driving the output line. All these components have been subjected to extensive tests of radiation hardness in different radiation environments and bias conditions. Both noise increase, modification of the working parameters and sudden breakdown have been observed. The CAMEX 64 under bias condition stands only up to 20-30 krad and hence is the weakest point of the chain.