3 V Zener — what the ratings mean on the bench
The 1N6311: Nominal Zener voltage is 3 V at ±5% tolerance — tight enough for a reference rail in a low-voltage regulator or a protection clamp on a 3.3 V logic input. Rated for 500 mW continuous dissipation in the DO-35 axial package; at 3 V that works out to roughly 167 mA maximum Zener current, but the real limit is the junction temperature — the -65°C to 175°C operating range gives plenty of headroom in an industrial or automotive environment. Max impedance (Zzt) is 29 Ohms at the test current — a stiffer reference than a higher-voltage Zener in the same series, which matters when the load draws a few mA.
Package and field-fit
DO-204AH (DO-35) glass axial package, through-hole mount — the same footprint as a 1N4148 signal diode, so it drops into an existing board layout without a pad change. Reverse leakage is 30 µA max at 1 V reverse — low enough that it won't pull down a high-impedance node in a battery-powered circuit. Forward voltage is 1.4 V max at 1 A — not a rectifier, but the spec confirms the die can handle brief forward current without damage if the diode is accidentally reverse-biased.