Draw the energy band diagrams of $p$ -type and $n$ -type semiconductors. 

If the emitter and base of $n-p-n$ transistor have the same doping concentration, explain how will the base and collector current be affected ?

Draw the circuit diagram of a half-wave rectifier using a $p$-$n$ junction diode.

Draw the circuit diagrams of $pn$ -junction in forward and reverse bias.

What type of biasing does give a semiconductor diode very high resistance ?