TO-121 NPN Bipolar Junction Transistor

#ComponentsCloseUp No. 285: TO-121 Transistor
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*** Quick Facts! ***
Manufacturer: Unknown
Part Number: Unknown
Package Size: TO-121
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I don’t know much about this part, besides that it is a transistor in the TO-121 style package. Specifically, it is another NPN silicon Bipolar Junction Transistor, and that's about all I know. I haven’t been able to find any other TO-121 style parts during my search, and since there isn’t any markings on the parts other than a 3-digit stamped number, I have no idea who made them.
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If you have any ideas as to who made them or what they were used in, I’d love to hear it! I’ll keep digging, and I’ll update this post with any further information that I find.

[dkhking]

It is an RF power transistor. Hint, the leads would solder to a stripline.

[rayoflight]

They look like RF output transistors, possibly in the UHF range, say the 2N4427 or the 2N3866.
They were invented for the radar used to land on the Moon. They are always been very expensive because of the segmented structure of the chip to reduce the parasitic capacitance, and thick bonding wire to reduce parasitic inductance.
In the '80s, some people used them in parallel to build FM broadcast transmitters. They work well in UHF, but they need tuned base coupling and tuned output load. They are a fantastic piece of technology to this day...

[dougrogan]

I have no idea why i watch these, it's not like I will ever use this info, but I like it and can't stop

[YSPACElabs]

Based on the package and thick wire bonds, I'm guessing it's a high (ish) power RF amplifier transistor.

[jaybird]

Looks like some high frequency power transistors ive seen in old RF equipment.

[GardenofEdens]

better explanation than i had ever been given in an electronic class. well done sir, i love looking into the parts we use do not open .

[bobweiss]

The stripline package suggests use at RF frequencies. Looks like it should be good for a few watts, at least...

[KathrynsWorldWildfireTracking]

_Howard Carter and Lord Carnarvon peer into the Transistor by flickering candlelight._
Carnarvon: "What do you see!?"
Carter: _Gold...everywhere, the glint of gold!!!_

[DeathMetalDerf]

It's been a very, very long time since I've seen one of those in anything I've opened up to repair or salvage for parts. A very long time indeed. If memory serves, those things are all about heavier-duty circuits that require a lot of switching, probably out of an RF amp transistor.

[MadScientist]

That's a power RF transistor, for things like handheld 2 way radio etc, used in the final of the transmitter.

[kc]

The reason those devices are so large is because they're designed to carry significant electrical voltages and currents. I used to use a transistor of this type (or similar, I can't remember the exact number) in a 12v model railway (railroad) controller that I built in the 1980's, which simulated loco throttle, coasting and braking effects. It worked pretty well, and was a lot more realistic than the standard rheostat-based controllers around at the time.
A transistor lke this is often attached to a heatsink to dissipate the heat load that 12v can cause.

[ronny]

Great, I love your Videos with explanation and illustration where B/C/E are present on the transistor. Makes it really easy to understand the main concept.

[EmilFr]

I used one of those, RF power transistor, (same package, don't know the part name though) last year to build an FM transmitter as the final assignment in RF class for my electronics technician journeyman certification. Also used one four lead one in the same package.
Don't really remember what the fourth lead was for though, but it was also a RF power transistor

[BlackEpyon]

I've got one of those component testers. I've no idea how accurate it is for measuring ESR on high voltage capacitors, , but it's otherwise pretty handy to have.

[BullProspecting]

I never seen them before.. They are loaded with gold!! Great find!
I been trying to find you something cool but compared to what you have i may have difficulty tryin to get you something better!

[danielash]

Base emitter collector a neat application for switching current 😅

[shane]

I love seeing really well made great quality electronic parts. And this definitely is something high quality made old because of the size but nevertheless I love how well made quality parts they are I love even more having them. It sad I don't get to see well quality made electronic parts very often anymore.

[IppiopaidFEEDBACK]

I never have any idea what this guy's talking about, but I love watching this videos. I'm addicted to them because my brain is geared towards mechanical things

[Peaches_NZ]

Man that's cool, would be cool to see how much current it can handle

[sowrabham]

Power transistor, that's why they have huge wires