15 V regulation point and 1 W dissipation ceiling
The 1N4744P/TR8 is a 15 V Zener diode in the standard DO-204AL (DO-41) axial-lead package, rated for 1 W continuous power dissipation. The 15 V nominal breakdown voltage sets the regulation point for clamping a supply rail or generating a reference — a ±10% tolerance means the actual Zener voltage can fall anywhere between 13.5 V and 16.5 V, so the downstream circuit must accept that spread without changing behaviour.
The 14 Ohms maximum Zener impedance (Zzt) is the dynamic resistance at the test current — a higher impedance means the Zener voltage shifts more with load current, so a low-impedance shunt is preferred for precision references.
Reverse leakage and forward drop — the fine print
Reverse leakage is 5 µA max at 11.4 V reverse voltage — well below the 15 V breakdown, so the diode stays off until the rail actually exceeds the Zener threshold. Forward voltage is 1.2 V max at 200 mA, which matters if the diode is used in a bidirectional clipper or as a flyback catch diode.