why forward voltage drop in normal silicon diode is around 0.7 volt and on what factors this depends
The forward voltage drop (often denoted as Vf) of around 0.6 to 0.7 volts in a silicon diode is a characteristic feature of these diodes. This value is a rule of thumb and can vary slightly depending on the specific diode and its construction. Several factors influence the forward voltage drop of a silicon diode:
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Material Type: The choice of semiconductor material plays a significant role. Silicon diodes have a Vf of approximately 0.6 to 0.7 volts. Other semiconductor materials, like germanium, have lower forward voltage drops, typically around 0.2 to 0.3 volts.
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Doping Level: The doping level of the semiconductor material also affects Vf. Doping is the process of intentionally introducing impurities into the crystal structure. High-doped diodes tend to have lower forward voltage drops.
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Temperature: Vf is temperature-dependent. As temperature increases, the forward voltage drop tends to decrease, and vice versa. This temperature dependence is due to changes in the semiconductor's intrinsic carrier concentration and mobility with temperature.
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Manufacturing Variations: Small variations in the manufacturing process can lead to slightly different forward voltage drop values even within the same diode type.
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Forward Current: The forward voltage drop is often specified at a specific forward current (e.g., 1 mA or 10 mA). At other forward currents, the Vf may vary slightly due to the diode's internal resistance and characteristics.
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Diode Type: Different types of diodes (e.g., rectifier diodes, signal diodes, Zener diodes) have slightly different characteristics, including Vf.
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Diode Size and Structure: The physical size and structure of the diode can impact Vf. Smaller diodes tend to have slightly higher forward voltage drops compared to larger ones. Additionally, specialized diodes, like Schottky diodes, have much lower forward voltage drops due to their unique design.