Shockley diode equation (small forward bias voltages)

Description

In electronics, a diode is a two-terminal electronic component with asymmetric conductance; it has low (ideally zero) resistance to current in one direction, and high (ideally infinite) resistance in the other. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. The Shockley diode equation or the diode law gives the I–V characteristic of a diode in real transistors, in either forward or reverse bias (or no bias).

For even rather small forward bias voltages the exponential is very large, since the thermal voltage is very small in comparison. The subtracted '1’ in the diode equation is then negligible and the forward diode current can be approximated as shown here.