A diode is a unidirectional two terminal device which is formed by the combination of p type semiconductor and n type semiconductor regions. Now, an ideal diode means a perfect diode which has all properties in their perfect sense without any flaws – not even the minuest.Usually the diodes operate either in forward-or reverse- biased condition. As a result, even the characteristics which are expected to be exhibited by the ideal diode can be analyzed separately for these two modes of operation.
Characteristics of Ideal Diode when Forward BiasedZero Resistance An ideal diode is expected to offer no resistance to the flow of current through it when working in forward biased mode. This means that the ideal diode will be a perfect conductor when forward biased. From this property of the ideal diode, one can infer that the ideal diodes do not have any barrier potential. This in turn leaves one to wonder on whether they possess depletion region or not. The reason behind this thought is attributed to the fact that the resistance offered is due to the presence of immobile charges which dwell in the depletion region of the diode.
Infinite Amount of Current This property of the ideal diode can be directly implied from its previous property which states that the ideal diodes offer zero resistance when forward biased. The reason can be explained as follows. In electronic devices, the relationship between the current (I), voltage (V) and resistance (R) is expressed by Ohm’s law which is stated as I = V/R. Now, if R = 0, then I = ∞. This indicates that there is no higher limit for the current which can flow through the forward-biased ideal diode.
Zero Threshold Voltage Even this characteristic of the ideal diode under forward biased state can be inferred from its first property of possessing zero resistance. This is because, threshold voltage is the minimum voltage which is required to be provided to the diode so as to overcome its barrier potential and to start conducting. Now, if the ideal diode is void of depletion region itself, then the question of threshold voltage does not arise at all. This property of the ideal diode makes them conduct right at the instant of being biased, leading to the green-curve of Figure 1 which shows the diode characteristics.