The TL431 is a three?terminal programmable shunt regulator diode. This monolithic IC voltage reference operates as a low temperature coefficient zener which is programmable from Vref to 36V with two external resistors. They exhibit a wide operating current range of 1.0mA to 100mA with a typical dynamic impedance of 0.22 ohms.
The characteristics of these references make them excellent replacements for zener diodes in many applications such as digital voltmeters, power supplies, and op-amp circuitry. The 2.5V reference makes it convenient to obtain a stable reference from 5.0V logic supplies,..
This is the BC337, an NPN silicon BJT (Bipolar Junction Transistor). This little transistor can help in your project by being used to help drive large loads or amplifying or switching applications. The BC337 is specifically rated at 50V and 800mA max.
Note: The BC337 is a drop-in replacement for the P2N2222A Transistor