This is a very common signal diode - 1N4148. Use this for signals up to 200mA of current.
Features
High Switching Speed: The primary feature is its rapid switching capability, with a reverse recovery time of typically 4 nanoseconds, making it suitable for applications up to 100 MHz. Low Cost and Wide Availability: It is one of the most popular diodes, widely manufactured and inexpensive, making it a staple for hobbyists and professionals. Reliability: The diode is hermetically sealed in a glass DO-35 package, offering good durability and stability across a wide operating temperature range (-65°C to +175°C). Low Capacitance: It has a very low junction capacitance, around 4 picofarads (pF), which helps maintain signal integrity in high-frequency circuits. Polarity: The cathode end of the diode is indicated by a black or colored band on the glass body.