NPN bipolar junction transistors make a good current source (technically a current sink). A resistor from the emitter to ground will set the current based on it’s resistance and the voltage across it (Ohms law). The voltage across the emitter resistor will be the voltage at the base, minus the 0.6V base to emitter drop.
- 014 NPN BJT switch improved 555 timer output NE555
- 015 NPN BJT emitter follower common collector voltage enhancement
- 017 PNP BJT current source set with zener diode
- 018 NPN BJT Schmitt trigger plus capacitor timed off circuits
Video covering NPN BJT current source and diagram
A lot of the components that I use are in this diode and transistor semiconductor kit.
Electronics course 16 current source circuit NPN BJT zener diodes trimpot light dependent resistor
Power supply I use in my videos.
Kit that has everything you need to learn basic electronics and Arduino.