1N4148

The 1N4148 is a general-purpose silicon junction diode encapsulated in a glass SOD27 (DO-35) package. It is a high-speed switching junction diode, which consists of a slab of p-type and an n-type semiconductor material in close contact with each other. This diode has wide operating parameters, which makes it suitable for a range of uses involving power and small signal applications. It became extremely popular due to its fast switching speeds, which is never more than 4 ns. Fairchild Semiconductor, NXP, NTE, and On Semi manufacture it. Many firms in China also manufacture cheaper equivalent versions of this diode, however I experienced screwy reverse recovery times on some batches. The reverse recovery time of a diode is the time it takes for the diode to change its state from reverse bias to a forward bias conduction. Usually larger bulkier diodes used in rectifier applications have a longer reverse recovery time.

SMD

The surface-mount device (SMD) equivalent is the LL4148 by Fairchild Semiconductor, which is in the SOD80 package.

Diode Specification

• Forward Voltage: 1 V when forward current is 10 mA
• Capacitance: 4 pF
• Breakdown Voltage: 100 V
• Leakage Current: 25 nA
• Switching Speed: 4 ns
• Power Dissipation 500 mW
• Continuous Reverse Voltage: 100 V max
• Repetitive Peak Reverse Voltage: 100 V max
• Repetitive Peak Forward Current: 450 mA max
• Mass: 105 mg
• Cathode Band Colour: Black
• Glass Capsule Length: 3.4 mm
• Glass Capsule Diameter: 1.75 mm
• Equivalent Diode: 1N914

Applications

• Small signal switching
• Rectifier
• High-speed switching

Buy

These diodes are available from Maplin, eBay, RadioShack, and almost all online electronics stores. The current eBay price is around £1.20 for a quantity of 100 diodes.

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