if the energy gap is between( 1.2 and 5) eV this is a O conductor: semiconductor insulator

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A 10V zener diode is used to regulate the voltage across a variable load-resistor. The input voltage varies between 13V and 16V and the load current varies between 10 and 85mA. The minimum zener currrent is 15mA. Calculate the value of series resistance, Rs.

A power diode used in a cell phone tower power supply dissipating power during the conductionprocess requires its junction temperature on not to exceed 180 degrees C. The power diode data sheet givesconduction-state voltage drop of 1.8V and for the DO-4 diode case, the junction-to-case thermal resistance, R-theta , jcis 0.8 degrees C/W. The diode is mounted over a heat sink having thermal resistances, case-to-sink R-theta,cs = 0.3degrees C/W and sink-to-ambient R-theta, sa= 0.6degrees C/W. Calculate the maximum current that diode can withstand safely without overheating if theambient temperature is 30 degrees C. Calculate the difference of temperature from case to sink. If the design requires to limit the junction temperature to 150 degrees C, select a value of R-theta,sa for aheat sink which should be used.