WEE Technology Company Limited

Manufacturer of Surface Mount (SMD) and Through Hole (DIP) Diodes & Rectifiers

1N indicates that the device has a 1 PN junction. Similarly, American type diodes all start at 2N because they have two PN junctions. 

Usually this product starts with several PN series and is developed in the United States. 4148 is just something like a serial number, and its number has no practical significance. LL4148 is a SMD version of 1N4148, Don't know exactly what LL means.

LL4148 usually refers to the glass-sealed cylinder LL-34 package (SMD Type, pinless).

1N4148 usually refers to DO-35 glass seal, axial pin, plug-in. It can be taped or packed in bulk.

1N4148 is a small high speed switching diode. The switch is relatively fast. It is widely used in circuit with high signal frequency for one-way conduction isolation, communication, computer board, TV circuit and industrial control circuit.

All of them are fast switching diodes, but they are packaged differently in order to suit for various PCB soldering patterns.

1N4148 is DO-35 plug-in through hole package, LL4148 is miniMELF chip SMD package, the two can be completely used alternately under low operating current.