Starting Electronics

Diodes

II

Maths

Although diodes are non-ohmic, this doesn't mean that

their operation can't be explained mathematically (just

as Ohm's law or, V = IR, say is a mathematical formula).

Diodes,

in

fact,

follow a relationship every bit as math-

ematical

as Ohm's law. The relationship is:

I

= li^-1

Η

kT

where I is the current through the diode, is the satura-

tion reverse current, q is the magnitude of an electron's

charge,

k is Boltzmann's constant, and Τ is the absolute

temperature in degrees Kelvin. As q and k are both con-

stant and at room temperature the absolute temperature

is

more or less constant, the

part

of the equation q/kT is

also

mor