give the v-I characteristic of a pn junction diode?

I = Io [ 1 - e^(v/(nV))]

here I = current through the pn juction diode

Io = reverse saturation current

v = voltage across the diode

n = a constant, value ranges from 1 to 2. It depend on the fabrication of the diode.

V = thermal voltage = kT/q

T = temperature in kelvin scale

k = Boltzman constant

q = electron charge = -1.6 X 10 ^ -19 C

the circuit diagram is very simple, draw a diode is series with a voltage source. Hope this can help. Check any microelectronics book for more information. I recommend " Microelectronic Circuits by Sedra/Smith"