ELEC95009 DevicesLecturer(s): Prof Tom Pike Aims
(1) To review the operation of diodes and bipolar junction transistors.
(2) To extend knowledge on bipolar devices to include the influence of recombination. (3) To investigate the physical mechanisms underlying the delays and speed limitations of the devices. (4) To extract equivalent circuit models for the devices. Learning Outcomes
Students should be able to
(1) Explain qualitatively the mechanisms of electronic conduction in bipolar devices, and calculate relevant quantities from given data. (2) Calculate and explain DC current-voltage behaviour of diodes and BJTs, given their geometry and material properties. (3) Explain the influence of excess minority carrier recombination of the performance of the devices. (4) Explain the large signal behaviour of the devices from the internal storage of charge. Syllabus
1. Revision on semiconductor devices
Last year you studied the DC behaviour of metal-semiconductor, metal-oxide-semiconductor and semiconductor-semiconductor junctions. We looked at basically three devices: the pn junction, the MOSFET and the basics of the BJT. We will start the course with reviewing the basic device DC operation concepts of the pn diode and the BJT because this year we will focus on bipolar devices. For more extensive information on MOSFETs please see the 3rd year Advanced Electronics Devices course . 2. Long pn diode In contrast to the “short” devices we’ve studied in the first year, this year we will introduce recombination processes and check how that influences the device behaviour. These devices will be referred to as “long” devices. Although an important characteristic of semiconductor devices is their fast response time, some delays do occur. We will investigate the physics behind the delays and investigate the resulting switching characteristics. The concept of a fast switching majority carrier device and a “slowly” switching minority carrier device will be made clear. 3. The BJT An npn or pnp junction is the basis for the bipolar junction transistor (BJT). Based on our knowledge of pn junctions, the DC functioning of a BJT will be described. As in pn junction, minority carriers will play an important role in the conduction mechanism of the BJT. We will look explicitly at the short BJT and discover that calculating the currents in this particular configuration is very straightforward. Switching of the BJT will also be studied and methods to reduce the delay discussed. Exam Duration: 1:30hrs Exam contribution: 100% Coursework contribution: 0% Term: Spring Closed or Open Book (end of year exam): Closed Coursework Requirement: Non-assessed problem sheets Oral Exam Required (as final assessment): no Prerequisite module(s): None required Course Homepage: https://bb.imperial.ac.uk Book List:
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