RF Transistor 2sc2290, uses?

[rwgast_lowlevellogicdesin]

http://pdf.datasheetcatalog.com/datasheet/toshiba/1465.pdf

So I came across this in a box full of pulled parts, not sure if it works. It has four leads, a base, a collector and two emitters. One of the emitter pins has been torn off or removed, there is a bit of copper flush with the transistor body though. If need be I can probably solder a new pin/pad on, viewing google pics it looks as if the second emitter is usually just grounded.

So I have never seen a 4 pin transistor before, whay does it have two emitters? Before I googled it I thought it was an old LNA or something. The example schematic in the data sheet only shows one emitter output, im also not even sure what this circuit does. Im also not sure what this does, im guessing it amplifys signals from two to thirty megahertz? But is it for TX and RX or just RX I only see it on output stages in pictures. These transistors in used condition go for about 30 dollars on ebay. I would like to work this in to an HF upconverter for an RTL SDR but im not sure how well it works or if it is even for RX. Like do you just connect this thing to the antenna?

[tec5c]

4 pin transistors are known as tetrode transistors. It depends on the application of the transistor as to what the extra pin is used for.

In the case of the 2SC2290, it is a power transistor for RF power amplifiers. In this case, the second emitter is connected in parallel to ground in order to reduce/eliminate parasitic inductances at higher frequencies.

Like do you just connect this thing to the antenna?

Not quite... If you're interested in HF amplifiers, take a read of Granberg's application notes. Found here: http://www.seboldt.net/k0jd/mot-an762.pdf

Also, are you familiar with the hybrid pi model for BJT's?

The test circuit in the datasheet is a simple amplifier which illustrates the gain and intermod. distortion products in the graphs below the schematic for the max. frequency limit of the device.

Edit: To provide link to said app note.

[rwgast_lowlevellogicdesin]

no im not familiar with the hybrid pi model, I will google it. Thank you for the info, I mostly use fets and and small signal common transistors for switching. When I need gain I tend to lean twords an opamp, so I guess you could say im a bit lame with transistors when used out of the digital domain. I mean I know how to bias one and set up a simple one transistor or pnp/npn combo to do minor amplification to maybe buffer, drive LED, or hold a relay open but thats about it. When it comes to analog I acually understand mosfets much more and tend to use them over transistors whenever possible.

I am also fairly new to original RF designs beyond filters and antennas. Ive been learning about pin diodes and triplexers recently but I have never bulit  a receiver or transmitter from scratch, mostly hacking on low noise filtered PSU's to lower noise floor and and preselectors is about what I know about RF electronics. I do a lot of SDR work as a hobby and am always looking for better front ends, I have just finished a project with a propeller chip connected to an antenna that uses a few counters to demodulate the AM band and output audio.

I usually buy my up/down converters and LNA's but I am getting more interested in what can do with hardware on the front end of an SDR. So my real question about this transistor specifically is, can it be used to amplify a input signal or is it to noisy and just meant for the TX side? I would be intrested in using it in a down converter im working on if it will work reasonably well as an RX amplifier. I dont have any plans to TX at 2-30 mhz so if it is more of a TX thing I will toss it back in the drawer along with the links you sent me and get to it at a later date. ALSO lastly is there a way to test this things with common tools? I dont have a meter with HFE since there only on crap DMMs, but I have a 2mhz signal gen and a scope. Maybe I could just use it to click a relay? If it does not work then its not even worth bothering with thinking of ideas for it! Any simple schematic would be appreciated that will allow me to test it without blowing it up, preferably one that doesnt need any pf caps or alot of specific nf caps.

[rfeecs]

Definitely just for the Tx side.
Also take note of the datasheet Beryllia warning.