Elmira Semiconductor
Elmira ELM291 NPN Switching Power Transistor, TO-220, Sealed
- 3 photos
Never used and never opened. Still in the factory tube, tray, reel or bag it shipped in, with the original date code intact.
New old stock, sealed on the grading scaleSend the quantity you need. You get a quote back with shipping before anything is charged.
Video
Filmed on the bench. Sound is stripped from product clips.
- 0:07
Specifications
| Specification | Value |
|---|---|
| Identification | |
| Part number | ELM291 |
| Manufacturer | Elmira Semiconductor |
| Condition | New old stock, sealed |
| Date code | Not recorded |
| Package | TO-220, in the original sealed Elmira package |
| Country of origin | Not recorded |
| Family | ELM291 |
| Stock number | PNBW4MCX |
| Overview | |
| Manufacturer part number | ELM291 |
| Brand | Elmira Semiconductor. A rebadged part, not an Elmira fabricated device |
| Cross reference | NTE291, which is the source of the figures below |
| Electrical | |
| Polarity and material | NPN silicon |
| Collector emitter voltage | About 120 V |
| Collector current | About 4 A |
| Dissipation | About 40 W with heatsinking |
| Transition frequency | About 4 MHz |
| Construction | |
| Package | TO-220. The metal tab is normally live |
| Condition | |
| Condition | Factory sealed. Never opened, so never tested |
About this part
Elmira Semiconductor was a replacement parts house rather than a fabricator, which is the useful thing to know before buying one of these. They catalogued devices under their own numbering so a technician could cross reference from whatever a piece of equipment specified, bought the silicon in, and put their name on the package. The ELM291 crosses to the NTE291, which is where the published figures come from.
Those figures describe a general purpose NPN power transistor: around 120 volts collector to emitter, 4 amps of collector current and about 40 watts with proper heatsinking, with a transition frequency near 4 MHz. That combination is a switch and a power amplifier rather than anything fast, and the TO-220 package is the one everybody recognises: a plastic body with a metal tab that bolts down, and the tab is electrically live on almost every device of this shape.
The package here has never been opened. That means the device has not been out, has not been tested, and has not been handled since it was put in. The card shows the dust, creasing and yellowing of its age. If you want the transistor rather than the sealed package, say so before ordering, because opening it is the one thing that cannot be undone.
Questions about this part
Did Elmira make this transistor?
No, and the listing says so rather than letting the name imply it. Elmira Semiconductor was a replacement parts house: it catalogued devices under its own numbering, bought the silicon in and put its name on the package. That was ordinary practice, and it is why the specifications here are quoted from the NTE291 cross reference.
Is the metal tab live?
On almost every TO-220 device, yes, and it is usually the collector. Anything the tab bolts to becomes part of the circuit, so a grounded heatsink needs an insulating washer and a shouldered bush unless the design intends the connection.
Will you open it to check the part inside?
Only if you ask, and it is not reversible. Sealed is how it is being sold and it is what makes the package worth anything beyond the transistor. If you want a device you can inspect, say so before ordering and we will discuss it.
What is it good for?
Switching and power amplification at moderate speed. Four amps and forty watts with a heatsink is a useful envelope, and four megahertz says it is not a high frequency part. Think supply regulation, motor and relay driving, or an audio output stage of the period.