Ideal Model
We have been seen that the diode acts essentially as a switch: on while forward biased, off while reverse biased. The ideal diode characteristic is indicated in diagram B. Equivalent to this is the ideal diode model, diagram Ba.
Dig B: Ideal diode characteristic.

Dig Ba: Ideal diode model.

While diode is reverse biased, we replace it along an open switch, and while the diode is forward biased, we utilize a closed switch.