Radiation Testing of Linear Microcircuits

A study was made to determine the effects of fast neutron radiation on linear microcircuits. Both overall effects and individual components were studied. Circuits tested were two operational amplifiers and two gold-doped comparators. The primary results of the tests were that one operational amplifier and the gold-doped comparators withstood up to 1014 nvt. The other operational amplifier withstood at least 3 × 1013 nvt. At these levels, gain was down about 50% on the comparators and input bias current was doubled. On the operational amplifiers, the input current showed a more severe degration than the gain because more feedback was used. Other circuit parameters showed little significant change up to the levels at which the gain was halved. By measuring common-base current-gain degradation at different current levels, it is shown that both base transport factor and emitter efficiency degrade with radiation. It has been determined that diffused resistors show little change up to 1015 nvt. Since current design utlizes resistor ratios instead of absolute values, the effect is further reduced. Avalanche breakdown voltages increased due to higher resistivities as expected. Other component changes were small. A particularly interesting aspects of the study was to determine the sensitivity to ratiation of a wide-base device, the so-called lateral PNP. Tests showed that the device was more sensitive to radiation thatn the NPN structures. Betas decreased by an order of magnitude at 3 × 10 nvt. A vertical PNP also showed heavy degradation.