Embedded Systems SemiconductorsTransistorsDiodesSlide 4Diode ImpedanceRectifiers - how would you do it?RectifiersSlide 8Slide 9Zener DiodeDiodes - LEDsFlyback DiodeIR Bumper - Modulated TransmitterLaboratory for Perceptual Robotics – Department of Computer ScienceEmbedded SystemsSemiconductorsLaboratory for Perceptual Robotics – Department of Computer ScienceTransistorsactive components that can increase the power of a signalbipolar transistor:• Si (silicon) semiconductor - tetravalent, has 4/8 electrons in its outer most (valence) shell• P (phosphorus) - pentavalent, has 5/8 electrons in its valence shell, which implies it has an extra loosely bound electron• B (boron) - trivalent, has 3/8 valence electrons…it’s also conducting (has “holes” in the electron cloud) Silicon is special• doped with phosphorus becomes “N” type semiconductor• doped with boron becomes “P” type semiconductor• only semiconductor that forms an insulating oxide layerLaboratory for Perceptual Robotics – Department of Computer ScienceDiodescharge distribution+--+--non-conducting+--+--+--reversebias+--+--conducting+ --forwardbiasSiP Nanode+cathode--+--depletion regionLaboratory for Perceptual Robotics – Department of Computer Sciencediodes are rated by the amount of current they can handle• small signal diodes ~100mA• power diodes ~ 1000’s of Ampsand the maximum reverse voltage they can withstand• ~ 75-80VIf you can measure a reverse current --- bad diodeDiodes+--non-conducting+ --reversebiasI=0Iconducting+--forwardbiasRarrow pointsin the directionof current flowLaboratory for Perceptual Robotics – Department of Computer ScienceDiode Impedancebreakdownvoltage~75VreversebiasedI current through diodeV voltage drop across diodeKirchoff’s laws don’t applyif 10mA is flowing throughthe diode, Vd~0.5VforwardbiasedLaboratory for Perceptual Robotics – Department of Computer ScienceRectifiers - how would you do it?~RloadACVloadtLaboratory for Perceptual Robotics – Department of Computer ScienceRectifiersVloadtRload~ACtwo diode dropsLaboratory for Perceptual Robotics – Department of Computer ScienceRectifiersVloadtRload~ACrippleLaboratory for Perceptual Robotics – Department of Computer ScienceRectifiersVloadtRload~ACripple+5Vdiode clamp: when V >= 5.6V diode is conductingLaboratory for Perceptual Robotics – Department of Computer ScienceZener Diodelet current go through backwards, while maintaining a near constant voltageIf I > 20-50mA, “pop”+--IRVinvoltage regulatorVout ~zener voltage(5-6V)Laboratory for Perceptual Robotics – Department of Computer ScienceDiodes - LEDsIconducting+--forwardbiasRforward V ~ 1.5-2.5 Vcurrent must be limited to 5-20mAstress limit 20-50mA blue higher Vgreenyelloworangered longer wavelength red/greenpolarity indicators+ --Laboratory for Perceptual Robotics – Department of Computer ScienceFlyback Diodetransistor opens:V=L dI/dt creates large (negative) polarization of the inductor, overstressing the transistor switchflyback diode clamps inductor voltage at (V+ 0.6) creates conduction path to dissipate the high tension chargeLaboratory for Perceptual Robotics – Department of Computer ScienceIR Bumper - Modulated TransmitterS1onoff+5VDC270 0.001