الفهرس | Only 14 pages are availabe for public view |
Abstract The present thesis is devoted in a trial to shed further light on some of the most important electronic devices; tunnel diodes (TDs) - made of (Gallium Arsenide; GaAs and Germanium; Ge) and back tunnel diodes made of Ge- as well, silicon unijunction transistor (Si-UJT). These devices are distinguished with negative differential resistance; (NDR) in their electrical characteristics. The electrical parameters of the different types of the proposed devices and their applications were studied. As an example; oscillator circuits based on TDs were investigated. For UJT, oscillator circuits; either sinusoidal or relaxation were studied and presented. As well, solar engines (BEAM-Type Robots) based on UJT either separate or combining with Sillicon Controlled Rectifier; (SCR) i.e. hybrid system were implemented. In this concern, various experimental work and different electronic software packages [National Instruments Multisim (NI Multisim) and Proteus] used for simulation were carried out. Moreover, applying computer programs for calculating theoretical equations using MATLAB language. Also, the work was extended to include the effect of different environmental conditions [low and high temperatures, as well, electronand gamma- irradiation (based on cobalt-60 source)] on such devices and their applications. Detailed experimental-and simulation-studies of the initial electrical characteristics for a wide spectrum of TDs were characterized. As an example, samples of GaAs-TDs: (AИ301г, 3И301B, AИ301σ, Au301A), samples of Ge-TDs (1N3712, 1N3716, 1N3718), and samples of Ge-back TDs (BD1, BD4, BD7) were chosen and investigated. As well, the most popular Si-UJTs (2N4870 and 2N2646) were utilized and their characteristics were carried out. I. Initial characteristics of the proposed devices: A. For TDs: - A set of electrical characteristic curves for TDs and back TDs were plotted. The main electrical parameters of both diodes were deduced.They are: the peak-, valley-and forward-voltages (VP, VV, VF), as well, the peak-and-valley-currents (IP, IV). Moreover, the other electrical parameters; voltage-and current-spans, voltage swing, peak-to-valley current ratio (IP/IV), output power (Pout) and finally, NDR were calculated. Comparing both devices TDs and back TDs, it was clear that the later had a suppressed Ip, hence, its characteristics approaches the conventional diode characteristics. B. For UJTs: 1. The emitter static characteristic curves (VE-IE) were plotted, for (2N4870 and 2N2646) Si-UJTs, at different interbase voltage (VB2B1) values. from which, the main electrical parameters (VP, VV, IP, IV, NDR and intrinsic stand-off ratio; η) were deduced and plotted for the two UJT types as a function of VB2B1. 2. The interbase characteristics (IB, VB2B1) were plotted at different emitter current values. from which, it is proved that the obtained relationships similar to the collector characteristics of a conventional transistor. 3. The interbase resistance of UJT (RBB) was determined for the two types, in case of open emitter. Its values were shown to be around 7.27 k and 6.29 k, respectively. II.The applications of the proposed devices: A. For TDs: Oscillator circuits were designed, implemented and tested based on GaAs-TD for low frequency operating range and based on Geback TD for both the low-and high- frequencies. For all the proposed systems, the output voltage waveforms were plotted, from which, the main parameters of the proposed oscillator circuit were deduced. The frequency and VP-P of Ge-back TD oscillator dependence on the bias voltage were investigated and plotted.B. For UJT: - Sinewave oscillator circuit was designed, implemented and tested, where the output voltage waveforms were plotted. from which, the main parameters of the proposed sinewave oscillator were deduced. - The relaxation oscillator circuit was designed, implemented and tested, where the output voltage waveforms were plotted, at different operating and circuit element conditions. from which, the main parameters of the proposed relaxation oscillator were deduced. - Two solar engine systems based UJT or UJT+SCR were designed, implemented and tested, where the systems operation were proved to be satisfactory. The designs of solar engines control circuits based on either UJT or UJT+SCR were implemented, and their output voltage, as well as, motor speed were tested under different illumination levels. In this concern, for 6.0 Volts motors, 1200 and 1720 rpm were obtained for the two systems whenever the polysilicon solar panel was illuminated up to around 50 klux. III. Temperature effects A.The characteristics of the proposed devices: a. For TDs: - For GaAs-TD and Ge-back TD, their electrical characteristics and deduced parameters were plotted under the influence of a wide temperature range (from -140 oC up to +101 oC, and from -81 oC up to +70 oC, respectively). 1. For GaAs-TD, the electrical parameters (IV, VV, VF and Pout), rates of changes due to temperature variations were shown to be; (+2.31 µA/oC, -0.44 mV/oC, -1.73 mV/oC and -0.54 µW/oC), respectively. In addition, IP was shown to be independent of temperature variations. 2. For Ge-back TD, the same parameters (IP, IV, VV, VF and Pout) were shown to be; (-0.049 µA/oC, +0.046 µA/oC, -0.66 mV/oC,-1.34 mV/oC and -5.84 nW/oC), respectively. Finally, for both diode types, VP was shown to be independent of temperature variations. 3. Considering the performance metrics of GaAs-TD and Ge-back TD, it was shown that for the first diode type, the rates of changes of its parameters (voltage span, voltage swing, IP/IV and NDR), due to temperature variations were shown to be; (-0.44 mV/oC, -1.73 mV/oC, -67.13 and -6.062 kΩ/oC), respectively. In addition, current span was shown to be independent of temperature variations. 4. For Ge-back TD, the rates of change due to temperature variations of the devices main parameters (current span, voltage span, voltage swing, IP/IV and NDR), were shown to be; ( -0.095 µA/oC, -0.66 mV/oC, -1.34 mV/oC, -27.86, and +0.255 Ω/oC), respectively. b. For UJT: - Concerning the operation of UJT within the temperature range from -133 oC up to +125 oC, the (VE-IE) characteristic curves were plotted. 1. The rates of changes of the main electrical parameters of UJT (VP, VV, IP, IV, NDR, and RBB), due to temperature variations were shown to be; (-2.91 mV/oC, -2.71 mV/oC, +4.99 nA/oC, -13.49 µA/oC, +8.49 Ω/oC, -0.73 oC-1 and +33.99 Ω/oC), respectively. B. The applications of the proposed devices: a. For TDs: - The output voltage waveforms of the oscillator circuit were plotted at different temperature levels, for GaAs-TD, within the range from -173 oC up to +100 oC, and Ge-back TD, within the range from -173 oC up to +65 oC. It is proved that both the frequency and peak-to-peak voltage (VP-P) are temperature independent.b. For UJT: 1. The output voltage waveforms of the sinewave oscillator circuit were plotted at different temperature levels from -156 oC up to +65 oC. The frequency was shown to be independent of temperature levels. On the other hand, VP-P was affected with temperature which followed Gaussian fitting, changes from around 4.0 Volts up to 4.72 Volts, where its initial value was 4.88 Volts. 2. For the relaxation oscillator circuit based on UJT, its output voltage waveforms were plotted at different temperature levels within the range from -165 oC up to +125 oC. from which, the rates of changes (dVP/dT and dVV/dT) due to temperature variations were shown to be; -6.55 mV/oC and -5.17 mV/oC. In addition, the frequency was increased from around 4.18 kHz up to 10.23 kHz. The charge time was decreased from around 225 µsec down to 88 µsec, but the discharge time was increased from 4.0 µsec up to 8.0 µsec. IV. Radiation Effects a. For TDs, (V-I) characteristic curves were plotted under the influence of different electron irradiation dose levels: For GaAs- and Ge-TDs: up to 3.73 MGy. Both diode types were shown to be insensitive to low irradiation levels, up to 1.0 MGy. For higher dose levels, the primarily failure mechanism in both device types is an increase on (IP and IV), while their (VV and VF) were shown to be decreased. 1. For GaAs-TD, the rates of changes of its electrical parameters (IP, IV, VP, VV, VF and POut), due to electron irradiation effects were shown to be; (+48.26 µA/MGy, +57.10 µA/MGy, -5.30 mV/MGy, -80.99 mV/MGy, -65.68 mV/MGy and -7.53 mW/MGy), respectively. 2. For Ge-TD, the rates of changes of the same parameters due to electron irradiation effects were shown to be; (+45.58 µA/MGy, +206.43 µA/MGy, +4.12 mV/MGy, -40.46 mV/MGy, -10.60 mV/MGy and -6.85 mW/MGy), respectively.3. Considering the performance metrics of GaAs- and Ge-TDs, it was shown that all the parameters were decreased as a function of the electron irradiation dose. 4. For GaAs-TD, the rates of change of its main electrical parameters (current span, voltage span, voltage swing and NDR), due to electron irradiation effects were shown to be; (-6.23 µA/MGy, -75.69 mV/MGy, -60.38 mV/MGy and -95.04 Ω/MGy), respectively. In addition, IP/IV was shown to be decreased from around 17.75 down to 3.95. 5. For Ge-TD, the rates of changes of the same parameters, due to electron irradiation effects were shown to be; (-160.09 µA/MGy, -44.58 mV/MGy, -14.72 mV/MGy and +11.92 Ω/MGy ), respectively. Finally, IP/IV was shown to be decreased from around 7.89 down to 1.31. b- For UJT, the dependence of (VE-IE) characteristic curves and electrical parameters on gamma exposure dose: up to 10 MGy, were plotted, where the following were recorded: 1. UJT parameters (VP, VV, IP, IV, NDR, and RBB) were shown to be decrease pronouncedly as a function of the irradiation dose, except its valley voltage, which, have an inverse trend, i.e., increases. 2. For the determined parameters, the rates of changes due to gamma irradiation effects were shown to be; (-195 mV/MGy, +95 mV/MGy, -0.54 µA/MGy, -70 µA/MGy, -71 Ω/MGy, -11.5 (MGy)-1 and -192 Ω/MGy), were deduced, respectively. |