The real diode is modelled as 3 components in series: an ideal diode, a voltage source and a resistor.

In such an ideal diode, if the diode is reverse biased, the current flowing through it is zero.

This ideal diode starts conducting at 0 V and for any positive voltage an infinite current flows and the diode acts like a short circuit.

The I-V characteristics of an ideal diode are shown below:

When forward biased, the ideal diode is simply a short circuit and when reverse biased, an open circuit.

The circuit is treated as a completely linear network of ideal diodes.

When reverse-biased, an ideal diode would block all current.

An ideal diode should have the following characteristics:

The actual transfer function of an ideal diode has been given at the top of this (non-linear) section.

I, the reverse bias saturation current for an ideal p-n diode is given by (Schubert 2006, 61):