The V-I characteristics of a silicon diode is shown in the Fig. . Calculate the resistsnce of the diode at `I_(D)=15mA` and ` V_(D)=-10V`.

Explanation

In forward characteristics of p-n junction at `I=15mA`, the diode characteristics is a straight line between `I=10mA "to" I=20mA`.
From the forward characteristics curve,
at `I=10mA, V=0.7V and at I=20mA,`
`V=0.8V.` Using ohm's law
`:. R_(fb)=(DeltaV)/(DeltaI)=((0.8-0.7)V)/((20-10)mA)=(0.1V)/(10mA)=10Omega`
From the reverse characteristic curve,
at `V=-10V, I=-1muA`
`:. R_(rb)=V/I=(-10V)/(-1muA)=10^(7)Omega`