Diode Bias Calculator
Analyze forward and reverse bias conditions. Calculate diode current, power dissipation, and understand the I-V characteristics of different diode types.
Calculate Diode Bias
Forward Bias
Diode is conducting current
📈 Diode I-V Characteristic Curve
The current-voltage (I-V) characteristic curve shows how diode current varies with applied voltage. This is fundamental to understanding diode behavior.
If vs Vf Characteristic Curves
Understanding the Curve
- Forward Bias Region: When V > Vf (threshold), current increases exponentially. The diode conducts.
- Reverse Bias Region: When V < 0, only tiny leakage current flows (microamps or less).
- Knee Voltage (Vf): The threshold voltage where conduction begins - varies by diode type.
- Breakdown Region: At very high reverse voltages, the diode breaks down (not shown, typically -50V to -1000V).
⚡ Diode Types Comparison
Different diode materials have distinct characteristics that make them suitable for specific applications.
| Property | Silicon (Si) | Germanium (Ge) | Schottky |
|---|---|---|---|
| Forward Voltage (Vf) | 0.6 - 0.7 V | 0.2 - 0.3 V | 0.15 - 0.45 V |
| Reverse Leakage | Very Low (nA) | Higher (µA) | Moderate (µA) |
| Max Temperature | ~200°C | ~85°C | ~125°C |
| Switching Speed | Moderate | Slow | Very Fast |
| Best For | General purpose, rectification | Low voltage drops, legacy circuits | High-speed switching, low loss |
| Common Part Numbers | 1N4148, 1N4001-1N4007 | 1N34A, OA90 | 1N5817-1N5819, BAT54 |
When to Use Each Type
- Silicon Diodes: Best for most applications - power supplies, protection circuits, general rectification. The 1N4007 is a workhorse for AC rectification.
- Germanium Diodes: Useful when you need low voltage drop and can tolerate higher leakage. Common in vintage radio detector circuits.
- Schottky Diodes: Ideal for high-frequency switching power supplies, reverse polarity protection, and applications where minimal power loss is critical.
🔄 Forward vs Reverse Bias Explained
Forward Bias Condition
A diode is forward biased when the positive terminal of the voltage source connects to the anode (P-side) and negative to the cathode (N-side).
- Current flows from anode to cathode
- Voltage drop across diode ≈ Vf (threshold voltage)
- Current is limited by the series resistor: I = (Vin - Vf) / R
- Diode acts like a closed switch with a small voltage drop
Reverse Bias Condition
A diode is reverse biased when the positive terminal connects to the cathode and negative to the anode.
- Virtually no current flows (only tiny leakage current)
- Diode acts like an open switch
- Used for protection, voltage blocking, and signal isolation
- If reverse voltage exceeds breakdown voltage, the diode can be damaged
The Bias Formula
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