BeginnerTopic 4 of 104Electronics & Embedded
Diode characteristics
Forward bias conducts above about 0.7 V for silicon; reverse bias blocks.
In depth
The Shockley equation I=I_s(e^{V/nV_T}-1) with V_T≈26 mV gives an exponential forward curve. Silicon knee ≈0.6–0.7 V, Schottky ≈0.3 V. Datasheets specify maximum forward current, reverse voltage and recovery time. Current must be limited with a resistor.
Key points
- Reverse leakage doubles about every 10 °C
- Schottky diodes switch fast
- Piecewise-linear models for hand analysis
ExampleAn LED supply at 5 V with 2 V drop and 20 mA needs 150 Ω.
What is Diode characteristics?
Forward bias conducts above about 0.7 V for silicon; reverse bias blocks.
Why is it important to understand diode characteristics?
Diode behaviour sets the voltage losses and protection behaviour in every power supply and signal circuit, so you must know the forward drop.
What is the forward voltage of a silicon diode?
About 0.6 to 0.7 V at normal current, depending on current and temperature.
Why use a Schottky diode?
Its lower forward drop of around 0.2 to 0.4 V reduces loss, and it switches faster than a standard silicon diode.
How is Diode characteristics used in practice?
Typical applications include estimating the voltage drop across a rectifier diode in a power supply, protecting an input pin from negative voltage with a clamp diode and choosing a Schottky diode to reduce loss in a low-voltage supply.
What should I learn before Diode characteristics?
Study "PN junction" first (topic 3 of 104 in Electronics & Embedded). It covers the groundwork this topic builds on.
What are the key points of Diode characteristics?
Reverse leakage doubles about every 10 °C. Schottky diodes switch fast. Piecewise-linear models for hand analysis.
Can you give an example of Diode characteristics?
An LED supply at 5 V with 2 V drop and 20 mA needs 150 Ω.
What comes after Diode characteristics?
The next topic is "Rectifier circuits", which builds directly on this one.
How difficult is Diode characteristics?
It is classed as Beginner in Electronics & Embedded (topic 4 of 104). It is an entry-level topic. It relies only on basic school mathematics and the ideas introduced earlier in this discipline.