Compendium of Circuit Effects in COTS Op Amps
T. Borel1,2, Laurent Dusseau2, University Montpellier, France,
1 University Montpellier, France, 2 CERN, Switzerland
Abstract
Operational amplifiers and voltage comparators are still widely used in space electronics. Often tested in standard conditions, they exhibit large degradation in the electrical and functional parameters. The degradation curves may exhibit unexpected shapes that are difficult to explain a with a black box approach. A good example is the degradation of the input bias current, which sometimes exhibits a bell shape or a peak. Those atypical behaviours may not be explained by physical mechanisms. They derive from compensation mechanisms at circuit level referred to as circuit effects. The compensation may be enhanced of attenuated depending on the type of architecture, the value of the currents in the current sources or the bias conditions during irradiation. A few examples of circuit effects observed on LM139, LM124 and OP400 will be presented and their impact discussed on the bias conditions to apply during TID testing.