1N4728A 3.3V Zener Diodes and Assortments
1N4728A identifies a nominal 3.3 V Zener diode in the 1N47xx axial family, commonly listed here in 1 W-class through-hole packs. The reverse breakdown voltage is specified at a particular test current, with a tolerance and temperature dependence, not as an exact 3.3 V regulated output at every current. Most products in this collection are multi-model selectors or multi-value kits: a heading that says 1N4728A does not make all its variants 3.3 V.
What the product options actually offer
- 1N4728A / 3V3 selections: look for a selected option explicitly marked 1N4728A 3V3 or 1N4728 3.3V in the 20-, 50-, 100- and larger-piece menus. Some sellers omit the initial “1” in N4728A or the suffix A in a selector; verify the body marking and exact manufacturer's datasheet before treating such shorthand as a specified replacement.
- Other 1N47xx grades: the same menus offer 1N4727A 3 V, 1N4729A 3.6 V, 1N4733A 5.1 V, 1N4742A 12 V and many additional values. They share a series but not the same breakdown voltage. Some variants display a model without any voltage, and a few descriptions disagree with a model's nominal grade; confirm the selected device from its technical documentation.
- Mixed kits versus single-value packs: 7-, 14- and other multi-value assortments include 1N4728A alongside different Zener grades. A 100-piece 1N4728A option is not equivalent to a 140-piece assorted kit even if both appear under a common product title. Read the variant and the included quantity per voltage.
- Packaging conflicts: listings describe some 1 W 1N47xx diodes as DO-41, while others call similar menus DO-35 or even include unrelated IC packaging fields. Do not infer the shipped body size, lead dimensions, power derating, compliance or provenance solely from the imported title. Verify the chosen component and its mechanical drawing before ordering for a fixed PCB layout.
Design and buying checklist
- Specify the actual 1N4728A grade and inspect its manufacturer datasheet for the Zener-voltage tolerance and stated test current; at different reverse current the voltage changes with dynamic impedance and may not remain 3.3 V.
- Check the source and load range of the intended circuit, allowable Zener current, worst-case dissipation and temperature-dependent power derating. A seller's “1 W” headline is not permission to dissipate 1 W in every installation.
- Match the axial package, lead spacing, cathode band and thermal environment; confirm exact part and pack count on the purchase order. A voltage reference Zener is not automatically a 3.3 V supply regulator or a transient-rated TVS.
Frequently asked questions
Is 1N4728A the same as 1N4729A?
No. The listed nominal breakdown grades are 3.3 V for 1N4728A and 3.6 V for 1N4729A. Check each part's full datasheet and test conditions before substituting.
Does a 1N4728A product title mean all choices are 3.3 V?
No. The variant menus also offer other Zener voltages, and some options are mixed kits. Choose the exact 3V3 option and confirm quantity.
Can I use a DO-35-labelled 1 W option as a drop-in DO-41 part?
Do not assume so. The imported package and power text is inconsistent in some listings. Resolve the actual part, mechanical dimensions and thermal rating before replacement.
Will this diode regulate a precise 3.3 V rail on its own?
No. Its reverse voltage is defined under test conditions and depends on current, tolerance and temperature. Use an appropriately specified regulator when a controlled rail is required.
