Instruction in analog electronics is an integral component of many physics and engineering programs, and is typically covered in courses beyond the first year. While extensive research has been conducted on student understanding of introductory electric circuits, to date there has been relatively little research on student learning of analog electronics in either physics or engineering courses. Given the significant overlap in content of courses offered in both disciplines, this study seeks to strengthen the research base on the learning and teaching of electric circuits and analog electronics via a single, coherent investigation spanning both physics and engineering courses. This dissertation has three distinct components, each of which serves to clarify ways in which students think about and analyze electronic circuits. The first component is a broad investigation of student learning of specific classes of analog circuits (e.g., loaded voltage dividers, diode circuits, and operational amplifier circuits) across courses in both physics and engineering. The second component of this dissertation is an in-depth study of student understanding of bipolar junction transistors and transistor circuits, which employed the systematic, research-based development of a suite of research tasks to pinpoint the specific aspects of transistor circuit behavior that students struggle with the most after instruction. The third component of this dissertation focuses more on the experimental components of electronics instruction by examining in detail the practical laboratory skill of troubleshooting. Due to the systematic, cross-disciplinary nature of the research documented in this dissertation, this work will strengthen the research base on the learning and teaching of electronics and will contribute to improvements in electronics instruction in both physics and engineering departments. In general, students did not appear to have developed a coherent, functional understanding of many key circuits after all instruction. Students also seemed to struggle with the application of foundational circuits concepts in new contexts, which is consistent with existing research on other topics. However, students did frequently use individual elements of productive reasoning when thinking about electric circuits. Recommendations, both general and specific, for future research and for electronics instruction are discussed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]