2N2222A by Texas Instruments is a small signal NPN bipolar junction transistor (BJT) with a max collector-emitter voltage of 40V and a max collector current of 0.8A. It is commonly used for switching applications due to its fast turn on/off times (35ns/285ns) and high transition frequency (300MHz).
The Vishay Intertechnology LL4148-GS08 is a glass diode with fast recovery time of 0.008 us and max reverse current of 5 uA. Ideal for applications requiring rectification, it has a breakdown voltage of 100 V and can handle a peak forward current of 2 A.
ULN2803ADWG4 by Texas Instruments is a peripheral driver with 8 functions, open-collector output characteristics, and built-in transient protections. It operates at temperatures ranging from -40 to 85°C and has a max supply voltage of 3V. Ideal for applications requiring sink current flow direction in a small outline package style.
Diodes Inc. BSS138-7-F is a N-channel FET with 50V DS breakdown voltage, 0.2A max drain current, and 3.5 ohm RDS(on). Ideal for switching applications in small outline packages with matte tin finish, operating up to 150°C peak reflow temp.