Lamps with screw bases have one lead-in wire soldered or welded to the
center contact and the other soldered or welded to the upper rim of the base
shell. Base shells are typically made of brass or aluminum.
Ceramic bases have internal leads welded to either metal contacts
or external lead wires.
Fluorescent Lamp Bases
For Preheat and Rapid Start lamps, four electrical contacts are
required, two at each end of the lamp. This is accomplished in the standard
line of lamps by use of a miniature bipin for T-5 bulbs and medium bipin
for T-12 bulbs. In Circline lamps, the cathodes are connected to a
four-pin base located between the junction of the two ends of the lamp. High
Output Lamps and Very High Output lamps have recessed double
contact (RDC) type bases. Slimline (Instant Start) lamps require
only two electrical contacts, one at each lamp end and have single pin bases.
All compact fluorescent lamps that do not have integral ballasts typically have
bases with 2 or 4 pins. The 2-pin lamps are
designed for preheat operation, and typically have an internal starter. The 4-pin
lamps are generally dimmable when used with a dimming ballast and are designed for electronic ballast operation. The 4-pin lamps typically
have no need for an internal starter.
Below are some common base types. To view more specific base types click a link
from the "Bases" menu at the top left of the page, or click on a light bulb base image below to
see an example of a product which uses that base.