Comparative Study on the Applications of BJTs and MOSFETs in some Modern Electronic Systems Under the Influence of Different Operating Conditions

Abstract

The aim of the present thesis is to shed further light on a comparative study of some applications (switch, RC- phase shift oscillator and DC-DC converter: boost and reverse self lift N/O Luo), based on two of the most common active electronic devices: bipolar junction transistors (BJTs) and metal oxide semiconductor field effect transistors (MOSFETs), under the influence of different operating conditions (high temperature ranging from room temperature up-to 135 oC and gamma radiation up-to almost 16 kGy). In this respect, extensive studies, and experimental works, were carried out on the tested devices; BJT type 2SC2120 connected in the common emitter configuration (CEC) and N-channel Enhancement Mode MOSFET type 2N6660. As well, for designing and implementing the proposed application circuits, a computer simulation using National Instrument Multisim Program Version 13.0 was applied. In this regard, the study includs the following: First: A detailed study of the electrical charactersics The static (I-V) characterstic curves (input / output for BJT, and transfer/output for MOSFET) were plotted. Besides, the dynamic characteristic curves, (C-V), namely: diffusion CD / transition CT capacitances, as well quality Q and - dissipation D -factors, and device impedance Z and phase angle ϕ for the two tested devices. From the static characterstic curves of the tested devices, several electrical parameters were calculated, at normal conditions, as well, under the infleunce of different environmentanl conditions. Concerning BJT, its DC current gain (hFE) value was calculated to be 79.4, calculated at room temperature and 240, at 85 oC, while its value was shown to be decreased down to 13, at 5.0 kGy. In Addition, for higher