Product Overview
Two Resistors Decide the Voltage, and This Three-Lead Package Does the Rest
Condition
New, and the photographed piece is representative of our stock. The black epoxy TO-220 body carries the National script N logo followed by 32HZ on the first line and LM317T P+ on the second, and that printing is crisp and fully legible in the photo. All three leads are straight and full length, with no solder on them and no bend or crimp from a previous board. The bare metal mounting tab carries the usual mounting hole and shows fine surface scratches in its finish. Sold each: the photo shows one unit, and marking parity across the other pieces in stock is not guaranteed.
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Product Overview
The LM317T is the TO-220 version of the classic three-terminal adjustable positive voltage regulator, and this one is a National Semiconductor part with the script N logo on the case. Instead of a fixed rail, it uses two external resistors to set the output, which adjusts down to 1.2V, and it is rated for a guaranteed 1.5A of output current. The published figures for the device include 80 dB ripple rejection, a current limit that stays constant with temperature, and short circuit protection on the output; the case is also marked P+, National's Product Enhancement designation. The package is the standard three-lead TO-220 with a bare metal tab and mounting hole for heatsinking, and on the LM317 the tab is tied to the output rather than ground, so it is not at chassis potential unless you intend it to be. Maximum input voltage, the input-to-output differential, and the thermal limits for your enclosure are not confirmed here - verify against the datasheet before use.
Key Features
- Three-terminal adjustable positive voltage regulator, output set by two external resistors
- Guaranteed 1.5A output current
- Output adjustable down to 1.2V
- Current limit constant with temperature
- 80 dB ripple rejection
- Output is short-circuit protected
- TO-220 package, three straight leads, bare metal tab with mounting hole for a heatsink
- Case marked with the National script N logo, 32HZ, and LM317T P+
Applications
- Building a variable bench supply where one regulator plus a pot has to cover everything from 1.2V logic experiments up to the rail your transformer can feed
- Repairing vintage audio, test gear, or an instrument power board where the original adjustable regulator has failed and the replacement needs to be the same three-lead TO-220 shape
- Setting up a simple constant current source for LED strings or battery charging by tying a single resistor between the output and adjust pins
- Prototyping an odd rail a fixed regulator will not give you, such as 3.3V, 5V, or 9V from the same drawer part
Frequently Asked Questions
What exactly is printed on the part?
The first line reads as the National Semiconductor script N logo followed by 32HZ, and the second line reads LM317T P+. Those two lines are the whole marking on the printed face; no separate date stamp or country line appears there in the photo.
How low and how high can I set the output?
The device adjusts down to 1.2V with the standard resistor divider, and 1.5A is the guaranteed output current. The usable upper end depends on your input voltage and the input-to-output differential the part will tolerate, which is not confirmed here - verify against the datasheet before use.
Does it need a heatsink?
That depends on your input voltage, output voltage, and load, since a linear regulator burns off the difference as heat. The tab and mounting hole are there for that purpose. Note that the tab on an LM317 is connected to the output, not ground, so use an insulating pad if the heatsink is grounded.
Was this part tested?
We sell it as new stock and describe what the camera shows: crisp factory marking, straight full-length leads, and no solder or board residue. The electrical figures above are the published specifications for the device, not bench measurements taken here.
Why buy a few here instead of a bag of 100 somewhere else?
Because most jobs need one or three, not a hundred. This is a commodity regulator sold each, so you can take the single piece a repair needs, a couple of spares for the drawer, or a handful for a board run, and stop there instead of paying for a minimum lot that lives in a bin forever. Shipping is a flat $8, free once your order passes $28, and orders leave our Idaho warehouse the same or next business day.
The LM317 turned voltage into arithmetic: pick two resistors and you name the rail. This National-marked TO-220 is still waiting on your numbers.
