Detailed explanation of diode classification
As a fundamental component in electronic circuits, diodes can be classified into various types based on their materials, structures, and applications. Each type has its unique functions and application scenarios in circuit design. The following is a detailed classification and characteristic analysis of diodes:
1、 Classified by material
Germanium diode (Ge tube)
Characteristics: Low conduction voltage (about 0.2V), suitable for low voltage scenarios, but with high reverse current and poor temperature stability. The operating temperature usually does not exceed 100 ℃.
Application: Originally used in detection circuits, it is now mostly replaced by silicon tubes and only exists in specific low-frequency or low temperature control requirements scenarios.
Silicon diode (Si tube)
Features: High conduction voltage (about 0.6V), low reverse current, high temperature resistance (up to 150-200 ℃), high reliability.
Application: Widely used in power rectification, voltage regulation, and high-frequency circuits, such as switching power supplies, industrial control equipment, etc.
2、 Classified by structure
Point contact diode
Construction: Metal needles contact semiconductor chips to form tiny PN junctions with small junction capacitance.
Characteristics: Suitable for high-frequency and low current scenarios (such as detection), but with weak withstand voltage and current capability.
Surface contact diode
Construction: The PN junction has a large area, allowing for high current to pass through.
Characteristics: Mainly used for rectifier circuits (such as alloy type, diffusion type), but with poor high-frequency performance.
Planar diode
Construction: A flat PN junction is formed through oxide film shielding technology, with high stability.
Features: Suitable for switch circuits and high-frequency applications (such as Schottky diodes), with long lifespan and stable performance.
Schottky diode
Construction: Metal semiconductor junction replaces traditional PN junction.
Features: Extremely short reverse recovery time (nanosecond level), forward voltage reduction (0.3V), suitable for high-frequency switching and low-voltage high current rectification.
Other structural types
Key type diode: Between point contact and alloy type, suitable for switching and detection.
Desktop diode: retains the PN junction through corrosion process and is commonly used in low current switch circuits.
3、 Classified by purpose
Rectifier diode
Function: Convert AC power to DC power, typical models such as silicon rectifier bridge QL series.
Features: High voltage resistance (up to 3000V), high current (several amps to tens of amps).
Zener diode (Zener diode)
Function: Utilizing reverse breakdown characteristics to stabilize voltage, temperature coefficient is divided into positive/negative categories.
Application: Power supply stabilization, reference voltage source, such as 2CW series.
Switching diode
Function: Fast conduction/cutoff, used for logic circuits and high-frequency switches.
Representative: Schottky diode (SBD) and 2CK series, with response times as short as nanoseconds.
Detector diode
Function: Extract low-frequency components from high-frequency signals, such as amplitude modulation and detection in radios.
Features: Germanium material point contact type (2AP series), operating frequency up to 400MHz.
Varactor diode
Function: The junction capacitance varies with the reverse voltage and is used for tuning and frequency control.
Application: Automatic Frequency Control (AFC) in TV Tuners and RF Circuits.
Light Emitting Diodes (LEDs)
Function: Convert electrical energy into light energy, covering the visible to infrared wavelength range.
Development: White LED drives the lighting revolution and is applied in displays, backlighting, and smart devices.
Transient Voltage Suppressing Diode (TVS)
Function: Quickly absorb surge voltage and protect sensitive circuits.
Parameters: Peak power (500W-5000W), response time in picoseconds.
PIN diode
Function: Variable impedance at high frequencies, used for microwave switching and signal modulation.
Features: Impedance varies with bias voltage, suitable for RF front-end design.
Avalanche diode
Function: Utilizing avalanche breakdown to generate high-frequency oscillations for microwave signal sources.
Application: Oscillatory circuits for radar and communication equipment.
Tunnel diode (Enozaki diode)
Function: Based on quantum tunneling effect, used for high-speed switching and low-noise amplifiers.
Features: Negative resistance characteristic, operating frequency can reach millimeter wave.
4、 Special purpose diode
Freewheeling diode: protects inductive loads and prevents reverse electromotive force from damaging circuits.
Damping diode: used in the TV scanning circuit, with high-frequency rectification function.
Double base diode (single junction transistor): used for oscillation and timing circuits, with good temperature stability.
The classification of diodes is based on various criteria, with materials determining basic performance (such as temperature resistance and conduction voltage), structure affecting frequency and power characteristics, and usage directly related to circuit functional design. When selecting, factors such as forward pressure drop, reverse recovery time, withstand voltage, and working environment should be comprehensively considered. For more technical details, please refer to industry materials or brand specifications.
