PIN Diode BasicAPPLICATION NOTE PIN Diode Basics Introduction Basic Theory―Variable Resistance A PIN diode is essentially a variable resistor. To determine the value of this resistance, consider a volume comparable to a typical PIN diode chip, say 20 mil diameter and 2 mils thick. This chip has a DC resistance of about 0.75 M . Note: 1 mil = 0.001 inches. In real diodes there are impurities, typically boron, which cannot be segregated out of the crystal. Such impurities contribute carriers, holes or electrons, which are not very tightly bound to the lattice and therefore lower the resistivity of the silicon. The resistivity of the I region and thus the diode resistance is determined by the number of free carriers within the I region. The resistivity of any semiconductor material is inversely proportion……