Difference between Ideal and Practical Diode

Explore the key difference between ideal and practical diode, including forward voltage drop, reverse current, and breakdown voltage. This article provides a clear tabular comparison to illustrate how theoretical and real-world diodes differ in performance and behavior.

Diodes are fundamental components in electronics, used extensively for their ability to control the direction of current flow in circuits. To understand diodes thoroughly, it’s essential to differentiate between the theoretical model of an ideal diode and the real-world behavior of practical diodes. This article explores these differences, detailing how they impact electronic circuit design and functionality.

Ideal Diode

An ideal diode is a theoretical model used to simplify circuit analysis. It acts as a perfect conductor when forward-biased and a perfect insulator when reverse-biased, with no intermediate states. This model helps in understanding the basic function of diodes without the complexities introduced by real materials. The VI characteristics of the ideal diode are given below.


Practical Diode

A practical diode, on the other hand, is a real electronic component manufactured from semiconductor materials like silicon or germanium. It exhibits several non-ideal behaviors due to its physical properties, manufacturing imperfections, and limitations of the semiconductor material. The VI characteristics of the practical diode are given below.

practical diode-vi-characteristics

Differences in Characteristics

Here are the key differences between an ideal diode and a practical diode, explained through their electrical characteristics:

  1. Forward Voltage Drop: In an ideal diode, there is no voltage drop when it is forward-biased; it behaves like a short circuit. Practical diodes, however, have a forward voltage drop (typically 0.7V for silicon and 0.3V for germanium), which must be accounted for in circuit designs.
  2. Reverse Current: An ideal diode has zero current in the reverse bias, acting as a perfect insulator. Practical diodes have a small leakage current in reverse bias due to minority charge carriers, which increases significantly at high temperatures or when the reverse voltage nears the breakdown voltage.
  3. Switching Speed: Ideal diodes switch instantly between conducting and non-conducting states with changes in voltage. Practical diodes have a finite switching time, affected by factors like capacitance and the time required for charge carriers to recombine.
  4. Breakdown Voltage: Ideal diodes do not break down or conduct in reverse bias under any circumstances. Practical diodes have a specific breakdown voltage at which they begin to conduct in reverse, sometimes leading to permanent damage if this voltage is exceeded without protection.

Tabular Comparison

FeatureIdeal DiodePractical Diode
Forward Voltage DropZero0.3V – 0.7V (depending on the material)
Reverse CurrentZeroExists, very small but increases with temperature
Switching SpeedInstantFinite, depends on material properties
Breakdown VoltageInfinite (no breakdown)Finite, specific to the diode’s design
Conduction ThresholdSharp transition at 0V( It has zero cut-in voltage)Gradual, starts at around 0.6V to 0.7V
LinearityCompletely linear (on or off)Non-linear characteristics
Temperature EffectsNonePerformance varies with temperature
RealizationIt is hypothetical and it can not be manufactured.It is practical to manufacture.
Resistance( Reverse Biased)Infinite resistanceVery high resistance
Resistance(Forward-bias)Zero resistanceLow resistance


Understanding the difference between ideal and practical diodes is crucial for students and electronics professionals. While ideal diodes serve as useful theoretical tools for learning and preliminary design, practical diodes with their non-ideal behaviors must be considered for accurate circuit design and analysis. This awareness ensures the reliability and efficiency of electronic devices in real-world applications.

  1. Varactor Diode
  2. Tunnel diode
  3. Zener Diode
  4. Laser Diode

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