Volt - Ampere PN Junction

Volt - Ampere PN Junction

1. What is this?

   • Is the curve between voltage across the junction and the circuit current.

2. Voltage

   • X axis

3. Current

   • Y Axis

4. Characteristics

   • Zero External voltage
     • External voltage is Zero
       • The potential barrier at the junction does not permit current flow
   • Foward bias
     • P-Type to positive terminal
     • N- thype to negative terminal
     • Potential barrier is reduced
       • The current start flowing when the potential barrier is altogether eliminated
         • Because
           • At some forward voltage (0.7 V for Si and 0.3 V for Ge),
         • Current increases
           • Increase in foward voltage
         • Once the external voltage exceeds the potential barrier voltage.
           • The pn junction behaves like an ordinary conduc- tor.
             • The current rises very sharply with increase in external voltage
   • Reverse bias
     • P type to negative termnal
     • N type to positive terminal
     • Potential barrier at the junction is increased.
       • Junction resistace becomes very high and no current flows
         • A very small current (of the order of μA) flows in the circuit with reverse bias