Electronics Handbook/Components/Diodes/PN

PN Diode

Construction	Symbol	I - V Curve
o-- P N --o

Characteristics

I V Curve

Conduction

When connect Voltage source's Polarities the same with Diode's Polarities . Diode does not conduct . No current can flow

When connect Voltage source's Polarities different with Diode's Polarities . Diode conducts . current can flow

Biasing Voltage

Diode does not conduct current with voltage below Conducting Voltage . Conducting voltage is the voltage at current equals to 1mA . For Si the conducting voltage is 0.3 v . For Ge the conducting voltage is 0.6 v . Diode's Conducting Voltage is denoted as V_d

V > V_d . Diode conducts current , I ≠ 0

V < V_d . Diode does not conduct current , I = 0

With this characteristic Diode can be used like a mechanical switch . Switch opens equivalent to V < V_d . Switch closes equivalent to V > V_d

Current

With voltage greater than Diode's Conductng Voltage . The change in current with change in voltage can be expressed as an exponential of Euler's constant e

$I=I_{o}(1-e^{\frac {V_{d}}{V}}t)$

When the value of V >> V_d ≈ 100v the I = I_o