SOP is generally a patch package form of devices with 8 pins or more (14, 16, 18, 20 pins, etc.) and is larger in size, while SOT is 5 pins or less (3 pins, 4 pins, etc.) ) The chip packaging form of the device is smaller in size.
For SMD chips, in the package name, the first letter indicates the type, and the following number indicates the number of pins. For example, SO-8 indicates an SO type package with 8 pins. And SSOP -16, correspondingly represents the 16-pin SSOP type package. As for the specific sizes of SO and SSOP, they are standardized and determined values. You can know by querying the corresponding information.
SMD Transistors, such as SOT-23 or SOT-223, represent SO type, T represents 3 pins, and the following 23 or 223 is the number of the package size, which has no practical meaning. You need to check the corresponding information for the specific size.
Some chips are in small packages, such as SOT-23-5, which means that this package is the basic size of SOT-23, but the number of pins is 5.
For chip diodes, such as SOD-123, it means SO type, D means 2 pins, and the following 123 is also the number of the package size. You need to check the corresponding information.