BSS138LT3G by Onsemi is a N-CHANNEL FET with a min DS breakdown voltage of 50V. It is used for switching applications and has a max drain current of 0.2A and max drain-source on resistance of 3.5 ohm.
LM2931AZ-5.0RAG by Onsemi is a Fixed Positive Single Output LDO Regulator with 5V nominal output voltage, 0.1A max output current, and 0.6V max dropout voltage. Ideal for applications requiring stable voltage regulation in temperature-sensitive environments up to 150°C.
ULN2803ADW by Texas Instruments is a peripheral driver with 8 functions, open-collector output characteristics, and built-in transient protections. It operates b/w -40 to 85 °C and has a max supply voltage of 3 V. Ideal for applications requiring buffer or inverter-based peripheral drivers with sink current flow direction.