Understanding Schottky Diodes: Explore Detailed Specs and a Wide Selection at Unikeyic Electronics

The Schottky diode is a metal-semiconductor diode created by the metal-semiconductor junction. It is named after W. H. Schottky, a German physicist. The Schottky diode is also referred to as a hot-carrier diode and Schottky barrier diode. It has a high switching speed and low forward voltage drop. It finds application in various switching, rectifying, and wave-shaping circuits. They are primarily employed in digital logic circuits and solar panels.

 

Fig. 1 - Construction and symbol of a Schottky diode

A conventional diode is made of a PN junction created by the combination of P-type and N-type semiconductor materials. There are majority and minority charge carriers in each region. When the diode is forward biased, the diode presents low resistance through which current flows through the junction. When the diode is reverse biased, it presents high resistance with only a minor leakage current. Due to this property, PN junction DIODES are utilized in switching and rectification. The I-V curve of a diode is non-linear as its DC resistance depends on applied voltage and current in both forward and reverse bias.

The forward voltage drop across a typical silicon diode is usually between 0.7V and 0.9V. For silicon diodes, the knee voltage (VK) - the voltage at which conduction starts - is approximately 0.6V to 0.9V. For germanium diodes, the knee voltage is about 0.3V. When reverse-biased, the diode prevents current from passing through it, with only a very small leakage current until the applied voltage is greater than the breakdown voltage.

 

Fig. 2 - A typical I-V Characteristic of a conventional PN junction diode

The Schottky diode differs significantly from the typical P-N junction diode in its structural composition. Instead of a P-N junction, a Schottky diode is formed by the junction of a semiconductor with a metal. The metal side acts as the anode, while the semiconductor acts as the cathode.

Anode: The metal side, made from a low-work-function metal, such as molybdenum, platinum, chromium, or tungsten.

Cathode: The semiconductor side, typically N-type silicon.

The contact between the metal and N-type semiconductor creates a barrier known as the Schottky Barrier. This barrier is responsible for the diode's unique characteristics.

 

The operation of a Schottky diode is based on the movement of majority carriers (electrons) across the metal-semiconductor junction. When forward-biased, electrons flow from the semiconductor to the metal, resulting in current conduction with minimal voltage drop. The absence of minority carrier injection leads to negligible charge storage, enabling faster switching times.

Key Characteristics of schottky diodes:

Low Forward Voltage Drop:

Typically, between 0.15V to 0.45V

Leads to higher efficiency

Fast Switching Speed:

Minimal charge storage

Suitable for high-frequency applications

High Efficiency:

Reduced power loss during operation

Low Reverse Recovery Time:

Enhances performance in switching applications

 

             Fig: 4 - Comparison of I-V Forward Characteristic of Schottky and Conventional Diode

I recently came across an excellent electronic components distributor — unikeyic Electronics. They offer a wide range of Schottky diodes from various manufacturers with competitive pricing and detailed technical specifications. Below are two notable Schottky diodes available on their site:

a) 1N5819

Reverse Voltage: 20V to 40V

Forward Current: 1A

Key Features:

1. Guard ring for overvoltage protection

2. Low reverse leakage current

3. High forward surge current capability

4. High-temperature soldering guaranteed: 250°C for 10 seconds at terminals

5. Lead-free and compliant with EU RoHS 2011/65/EU directives

Pricing: Available from multiple manufacturers on Unikeyic. The starting price is around $0.1223.

 

 

b) 1N5817

Key Features:

Guard ring for overvoltage protection

Low power loss

Extremely fast switching

High forward surge capability

Suitable for high-frequency operation

Solder dip: 275°C max for 7 seconds (per JESD 22-B106)

Typical Applications:

1. Low-voltage, high-frequency inverters

2. Freewheeling diodes

3. DC-DC converters

4. Polarity protection circuits

Pricing: Also offered by various manufacturers. The starting price is approximately $0.4485.

 

c) SS54 - SMD mount

Reverse Voltage: 20V to 100V

Forward Current: 5.0A

Key Features:

1. Metal-semiconductor junction with guard ring protection

2. Epitaxial construction

3. Low forward voltage drop

4. High current handling capability

5. Encapsulated in plastic material with UL 94V-0 flammability classification

6. Ideal for low-voltage, high-frequency inverters, freewheeling diodes, and polarity protection applications

Pricing: The Multicomp SS54 Schottky Barrier Rectifier is listed on Unikeyic Electronics with a starting price of $0.8644 for a minimum order quantity of 5 units.

 

d) BAS40-AQ (SOT-23 package)

Average Forward Current (IFAV): 200 mA

Forward Voltage (VF at 1mA): < 0.38V

Maximum Junction Temperature (Tjmax): 150°C

Repetitive Peak Reverse Voltage (VRRM): 40V

Surge Forward Current (IFSM): 600 mA

Reverse Recovery Time (trr): < 5 ns

Key Features:

Very high switching speed

Low junction capacitance

Low leakage current

RoHS (without exemption), REACH, and Conflict Minerals compliant

Typical Applications:

1. Signal processing

2. High-speed switching

3. Polarity protection

Pricing: The BAS40-AQ Schottky diode is available on Unikeyic Electronics with a starting price of $0.1725.

 

 Applications of Schottky Diodes

Schottky diodes are widely used in various electronic applications due to their low forward voltage drop and fast switching characteristics. Key applications include:

Power Rectification: Their low forward voltage drop makes Schottky diodes ideal for power supplies, improving overall efficiency.

Voltage Clamping: Used to protect circuits from voltage spikes by clamping excessive voltages.

Reverse Current and Discharge Protection: Commonly used in battery-powered systems to prevent reverse current flow and protect against discharge.

High-Frequency Applications: Thanks to their fast recovery time, Schottky diodes are suitable for RF circuits, mixers, detectors, switch-mode power supplies, and DC-DC converters.

Unikeyic Electronics offers a wide range of Schottky diodes, which you can explore on their official website.

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