SD2933

[Elopid]

Hey all,

I was recently given some SD2933 transistors but I can't see anything on the web in relation to any circuits for FM broadcasting. Has anyone ever used them and does anyone know of a schematic I can use for this device?

The data sheet shows it as a 30MHz device and says it good for up to 150MHz, I would really like to get something going with these devices as they are just one single fet transistor so would require a lot less parts than the double transistors BLF278, SD2932 and MRF151G (for example).

Failing that I'll just sell them on and replace them with the above transistors.

Thanks in advance, EloPiD

[Spokes]

Found an ST data sheet on the 2933 says it's a 1.6-54mhz device?

[Elopid]

Hi Spokes, thank you for your reply. What datasheet did you find that from?

The devices I have got are made by SGS Thompson (ST) and here is what that datasheet says:



Cheers, EloPiD

[Analyser]

If that's a picture of the actual transistors they're probably fakes; the Chinese silver bag is a dead giveaway, also you'll notice around the mounting holes there are indents where they've previously been in an amplifier amd spacers have compresssed the flange (new devices don't have those marks).

[Elopid]

Good evening Analyser,

I have no doubt you are right, no that was just a picture from the web but here are the actual devices below.

They do appear as you describe but I can't see any signs of them being previously used and they 'appear' new. I'd rather not remove one out of the sealed bag though because I'm probably going to sell them on. I've never seen an FM transmitter with these output devices inside, do you know if they are any good for what I need or shall I get rid of them?

- EloPiD -

[yellowbeard]

They look dinged up alright, however there is an application note on ST's site that specifically says "FM broadcast applications up to 150MHz".

Code: Select all

http://www2.st.com/content/ccc/resource/technical/document/application_note/07/e8/f6/20/61/db/43/d2/CD00004135.pdf/files/CD00004135.pdf/jcr:content/translations/en.CD00004135.pdf

That isn't helping find a circuit tho...

[Albert H]

The "Chinese" anti-static bag isn't ever indicative of them being "fakes" - even RS and Farnell use the same metallised plastic for their component bags to avoid static issues!

These are second-generation MOSFET devices. They will NOT tolerate overdrive or over-bias - you'll destroy the gate if you do either. I've had over 400W out at 98MHz with just on a Watt of drive, but I throttled them back to 250 Watts by reducing the drive and the supply voltage.

Heat sinking is crucial. So is an effective lowpass filter. A single-ended circuit with this device will produce lots if second and third harmonic, so you have to make sure that these don't get to the aerial

[Analyser]

Good evening Analyser,

I have no doubt you are right, no that was just a picture from the web but here are the actual devices below.

They do appear as you describe but I can't see any signs of them being previously used and they 'appear' new. I'd rather not remove one out of the sealed bag though because I'm probably going to sell them on. I've never seen an FM transmitter with these output devices inside, do you know if they are any good for what I need or shall I get rid of them.

]

You're quite right they do look new, and that's the thing, the Chinese have a way of reconditioning the leads by removing the solder and somehow getting them gold again, I'd love to know how they do it. Anyway, having said all that those you have there might be a genuine transistor becuase looking at the back you can see a circle cut in to the flange; the only transistors I've seen with that are the higher power SD FETs from ST Micro, they might not be a 2933 though (there's stuff like the 2941 etc).
With regards to a circuit, I think I've had a play with one a while ago. IIRC I got about 200w from it. Not sure if I made a schematic but I'll look for one over the next few days for you.

[OldskoolPirate]

Can we still get this schematic plz ?