Catalog / Diodes: Electronic Components Cheat Sheet
Diodes: Electronic Components Cheat Sheet
A concise cheat sheet covering various types of diodes, their characteristics, and common applications in electronic circuits. This guide provides a quick reference for students, hobbyists, and professionals working with electronics.
Diode Fundamentals
Basic Diode Operation
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A diode is a two-terminal semiconductor device that conducts current primarily in one direction (from anode to cathode) and blocks current in the opposite direction. |
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Anode (A): The positive terminal of the diode. |
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Forward Bias: When the anode is at a higher potential than the cathode, the diode conducts. |
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Reverse Bias: When the cathode is at a higher potential than the anode, the diode blocks current (ideally). |
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Breakdown Voltage: The reverse voltage at which the diode starts to conduct in the reverse direction. |
Key Parameters
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Forward Voltage (Vf) |
Voltage drop across the diode when conducting (typically 0.7V for silicon diodes). |
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Reverse Current (Ir) |
Small current that flows in the reverse direction when the diode is reverse biased (ideally zero). |
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Maximum Forward Current (If) |
The maximum current the diode can handle in the forward direction without being damaged. |
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Peak Inverse Voltage (PIV) |
The maximum reverse voltage the diode can withstand without breaking down. |
Types of Diodes
Signal Diodes
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Small diodes used for signal processing and switching applications. |
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Examples: 1N4148, 1N914. |
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Fast switching speed and low forward current capability. |
Rectifier Diodes
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Used in power supplies to convert AC voltage to DC voltage. |
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Examples: 1N4001 - 1N4007 (different PIV ratings). |
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Higher forward current and lower switching speed compared to signal diodes. |
Zener Diodes
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Operation |
Designed to operate in the reverse breakdown region, maintaining a constant voltage across them. |
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Applications |
Voltage regulation and overvoltage protection. |
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Example |
1N4728A (3.3V Zener), 1N4742A (12V Zener). |
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Note |
Specified by their Zener voltage (Vz) and power dissipation. |
Light Emitting Diodes (LEDs)
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Function |
Emit light when forward biased. |
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Colors |
Available in various colors (red, green, blue, yellow, white). |
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Applications |
Indication, illumination, displays. |
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Parameters |
Forward voltage (Vf) and forward current (If) are critical parameters. |
Schottky Diodes
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Low forward voltage drop and fast switching speed. |
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Used in high-frequency applications and clamping circuits. |
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Example: 1N5817, 1N5819. |
Diode Circuits and Applications
Half-Wave Rectifier
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A simple rectifier circuit that allows only one half-cycle of the AC voltage to pass through. |
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Output is pulsating DC with a significant ripple. |
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Efficiency is relatively low. |
Full-Wave Rectifier
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Center-Tapped |
Uses two diodes and a center-tapped transformer to rectify both halves of the AC cycle. |
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Bridge Rectifier |
Uses four diodes in a bridge configuration to rectify both halves of the AC cycle without a center-tapped transformer. |
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Output |
Provides a smoother DC output compared to the half-wave rectifier. |
Clipping Circuits
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Use diodes to clip off a portion of a signal above or below a certain voltage level. |
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Series clippers and shunt clippers are common configurations. |
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Used for signal shaping and protection. |
Clamping Circuits
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Function |
Shift the entire signal voltage by a DC level. |
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Components |
Typically consist of a diode and a capacitor. |
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Usage |
Used to set a specific voltage level for a signal. |
Reverse Polarity Protection
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A diode placed in series with the power supply to protect the circuit from reverse polarity connection. |
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The diode conducts only when the polarity is correct. |
Advanced Diode Concepts
Diode Models
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Ideal Diode Model |
Acts as a perfect switch, with zero forward voltage drop and infinite reverse resistance (theoretical). |
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Practical Diode Model |
Includes a forward voltage drop (e.g., 0.7V for silicon) and a small reverse leakage current. |
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Complete Diode Model |
Includes junction capacitance and reverse recovery time for more accurate simulation. |
Diode Specifications
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Datasheets provide detailed specifications of diode characteristics, including:
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Temperature Effects
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Forward Voltage |
Decreases with increasing temperature (approximately -2mV/°C for silicon diodes). |
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Reverse Current |
Increases with increasing temperature. |
Avalanche Diodes
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Designed to operate in the reverse breakdown region, similar to Zener diodes, but using avalanche breakdown. |
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Used for surge protection and high-voltage applications. |