Retina: Microcircuits for Daylight, Twilight, and Starlight Vision

Over the course of the day, light intensity can vary by 10 billion-fold, but a retinal ganglion cell’s spike rate can change only by 100-fold. To cover the huge intensity range, two fundamentally different retinal circuits are required: a cone bipolar circuit for transmitting graded photoreceptor signals and a rod bipolar circuit capable of transmitting binary signals. By using gap junctions, the two circuits can share key neural elements. Such an efficient use of circuitry is critical in a neural tissue that is constrained to be thin and transparent.

TOTAL DOSE EFFECTS IN LINEAR BIPOLAR INTEGRATED CIRCUITS

Electronics systems that operate in space or strategic environments can be severely damaged by exposure to ionizing radiation. Space-based systems that utilize linear bipolar integrated circuits are particularly susceptible to radiation-induced damage because of the enhanced sensitivity of these circuits to the low rate of radiation exposure. The phenomenon of enhanced low-dose-rate sensitivity (ELDRS) demonstrates the need for a comprehensive understanding of the mechanisms of total dose effects in linear bipolar circuits. The majority of detailed bipolar total dose studies to date have focused on radiation effects mechanisms at either the process or transistor level. The goal of this text is to provide an overview of total dose mechanisms from the circuit perspective; in particular, the effects of transistor gain degradation on specific linear bipolar circuit parameters and the effects of circuit parameter degradation on select linear bipolar circuit applications.