I. Introduction
Important knowledge and understanding of bipolar devices sensitivity to ionizing dose has been gained from the first studies where TID effects where investigated [1]–[6] to the more recent studies related to dose-rate effects [7]–[20]. Device physics and physical mechanisms in the oxide are used to explain the dose sensitivity, but recently it has also been suggested that, in the case of bipolar microcircuits, the combined effects of degradation in multiple transistors have to be considered to explain the complex degradation of electrical parameters observed at the circuit level after irradiation. These are known as the circuit effects [20]–[26]. The behavior of the electrical parameters of a microcircuit is generally observed after irradiation of the entire die. As a consequence all the devices on-chip are degraded and a detailed analysis of the degradation of transistors and sub-circuits, like the current sources, is required to explain the observed behavior of the entire circuit. This is a complex task because a bipolar microcircuit is an assembly of multiple bipolar transistors where each transistor may affect the behavior/biasing of neighboring transistors and also the electrical response of the entire circuit.