the valence band is partially empty and the conduction band is partially filled

the valence band is completely filled and the conduction band is partially filled

the valence band is completely filled

the conduction band is completely empty

if both inputs are zero

if either or both inputs are 1

only if both inputs are 1

if either inputs is zero

lowers the potential barrier

raises the potential barrier

increases the majority carrier current

increases the minority carrier current