Notes Flashcards
What is a crystal-lattice?
atoms of purified semiconductor materials that arrange themselves into a unique pattern
covalent bonding?
when adjacent atoms share their outer valence electrons to create a stable eight electron arrangement
How to make a semiconductor a better conductor?
by adding a small amount of impurity into the crystal-lattice (doping)
number of valence electrons in P-type?
three (trivalent)
common trivalent elements?
boron, aluminum, gallium
number of valence electrons for N-type?
5 (pentavalent)
common elements for pentavalent?
arsenic, phosphorus, antimony
How to dissipate heat losses?
mount semiconductors on aluminum sinks
What are rectifiers used for?
to convert AC into DC
half-wave rectification?
when only half of the AC input is converted to undirectional DC
Full-wave rectification?
When both alternations of the AC waveform are converted to undirectional DC
PIV rating must be greater than peak value, what is the calculation for 120v?
120v / 0.707 = 170v PIV
What is ripple frequency?
number of output pulses of DC is known as ripple frequency
How to achieve full-wave rectification?
using two different circuit configurations
Average value of an AC sine wave?
zero
levels of sin wave (top to bottom)
——Peak
_____ RMS 70.7%
_____ Average 63.4%
What is a zener diode and what does it do?
usually made from silicon, looks like normal foods but works in reverse direction
When is a zener diode used as a voltage regulator?
when in reverse bias
typical zener wattage ratings?
250mw to 50w
What can zeners not be tested with and why?
ohmmeter because the battery could be strong enough to break the voltage of the zener diode
key points to observe when using zeners as voltage regulators?
- circuit with a constant load but variable input
- connect zener diode for reverse bias operation
- use series current-limiting resistor
- ensure dc input exceeds zener voltage rating
Zener will only regulate if….?
variable input is higher than its own voltage rating
