Microelectronics Engineering
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Browsing Microelectronics Engineering by Author "Getachew, Alemu (PhD)"
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Item Analysis of the Effect of Presence of Magnetic Field in Photon-electron Interface(Addis Ababa University, 2021-11) Alema, Abraha; Getachew, Alemu (PhD)Electronics played a great role in storing, computing, and transmitting data. However, electronics had certain limitations in bandwidth, speed, power consumption, and electromagnetic interfering. Conversely, photonic provides advantages like large bandwidth, lower power consumption, and immune to electromagnetic interference. Therefore, to overcome the electronics limitations, electronics and photonics integration developed. Despite many advantages of the integration of electronics and photonics, the presence of an external magnetic field in photon-electron interfaces influences the performances of lasers and photodiodes. Those effects are well studied when lasers and photodiodes are separately subjected to the magnetic field in previous studies. However, the difference in the magnetic field effects on the output signal when both transducers are concurrently exposed to the field needs further study. Additionally, the influence of change in input signal frequency to the magnetic field effect on output signal when laser and photodiode are separately and simultaneously exposed also needs further study. To demonstrate the difference in magnetic field effect on the output signal when the frequency of input signal varies as well as both laser and photodiode concurrently exposed to magnetic field relative to separately subjected; experimental setup was prepared in the laboratory by connecting VCSEL and PIN photodiode with other devices. Then experiments were conducted at around room temperature. During experimentation, both transducers were individually and concurrently exposed to the static magnetic field oriented B//n and B┴n, at 3 kHz & 10 kHz. Then output voltage was measured and recorded at 0, 400, 600, 800, and 1000mT. The results were compared based on the rate of change in output voltage at different magnetic flux densities and frequencies. The magnetic field effect on output signal was found higher at 3 kHz compared to at 10 kHz for both VCSEL and PIN photodiode individually and concurrently exposed. Additionally, the comparisons made at a fixed frequency showed that the magnetic field effect on output signal was much higher when VCSEL and PIN photodiode concurrently exposed relative to individually exposed.Item Analysis of The Functional Variation of Cascaded Amplifier When Replaced with Their Spintronics Equivalents(Addis Ababa University, 2019-07) Ermias, Tewabe; Getachew, Alemu (PhD)Spintronics is a new technology that employs the spin degrees of freedom of carriers instead of electrons’ charge for storing and processing data. Either by using spins alone or by adding the spin degrees of freedom to the more established semiconductor technology, it is possible to enhance the functionality of the device greatly. In this thesis, two major things have been done. In part one, after studying literature reviews which were done on spin transistors, magnetic bipolar transistor models are proposed, Three quite different magnetic bipolar transistors are developed by incorporating magnetic impurities in all three regions. And the energy band edges of semiconductor device in the presence of magnetic impurities are calculated. In part two, the proposed spin transistors models are validated by employing on some application areas (Cascaded amplifier). The performances of magnetic bipolar transistors (i.e., using one of the models of spin transistors and the proposed ones) for multistage amplifiers are analyzed. In order to simplify the equivalent circuit for AC analysis, simplified re model for low frequency is used. And hybrid-π model is used for high frequency. Since each parameters in re model and hybrid-π model are function of spin polarization of carriers, the equivalent circuit models used in this thesis work quite well for spin based transistor. In this thesis it is able to come up with quite different types of magnetic bipolar transistors in which spin of carriers are the main controlling inputs. It is shown that the device’s parameters are function of the spin of electrons and holes, and the injected spin electrons in the emitter and collector. Contrary to the conventional bipolar transistor, the magnetic bipolar transistor models are capable of controlling current amplification factor and the density of minority of carries through spins of electrons and holes. As a result, the performances of cascaded amplifier are improved compared to the performances of the conventional transistor.Item Configurable Analog Circuit Synthesis and Implementation Kit: PCB Based Approach(2018-05-15) Abisa, Girma; Getachew, Alemu (PhD)The implementation of newly designed analog circuits in most cases is a merger of known analog circuit blocks. The testing of these analog circuits have challenges like schematic to prototype part discrepancy, being cumbersome, fragility and component value variation. Field Programmable Analog Array (FPAA), could be considered analog counterparts FPGA, have been used for the design and development analog circuits. FPAAs combine CAD tool with rapid prototyping of analog circuits. FPAAs are monolithic programmable and generic analog circuit building tools. In this paper a configurable PCB based analog circuit builder kit is to be designed and built as a possible rugged alternative to FPAAs. The need for this alternative is put forward to utilize the advantages of FPPAs in a more rugged and accessible analog circuit building. This kit contains real analog circuit components with configurable interconnecting switches on a single board. The building and validation testing of such a kit is performed in this research. It can handle more power and larger components. It contains on board power supplies and component banks. This kit could be instrumental in the education/training of analog circuit design both in academia and industry.