SEMITEC S-153T Constant Current Diode, 18mA, 4.3V max, 2-Pin SMD

Current Regulating Diodes (CRD), ATC Semitec

Constant Current Diode (also called current limiting diode, diode-connected transistor, or current-regulating diode) consists of a JFET with the gate shorted to the source. It functions like a two-terminal current limiter or current source (analogue to voltage limiting Zener diode). They allow a current through them to rise to a certain value, and then level off at a specific value.

Ideally suited for use as current regulators/ limiters, biasing elements and for use in linear ramp generators, staircase generators, etc.