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| 11911 | 2015-11-26 09:42:50 | bob_ledoux | Question: What SMT Transistor for Post-Mixer Amp | ||||||||||||||||||||||||||||||||
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The 2N5109 was commonly used as a post mixer amp at HF frequencies. It was powered with lots of current to preserve dynamic range. So what SMT transistors are being used for the post mixer amp function? bob-N7SUR | |||||||||||||||||||||||||||||||||||
| 11912 | 2015-11-26 11:03:04 | K5ESS | Re: Question: What SMT Transistor for Post-Mixer Amp | ||||||||||||||||||||||||||||||||
Here’s a link that discusses an SMT replacement for the 2N5109 if you haven’t already seen it.
http://www.mtmscientific.com/preamp.pdf
Mike K5ESS
11914
| 2015-11-26 12:25:33
| kb1gmx
| Re: Question: What SMT Transistor for Post-Mixer Amp
| there are a number of devices that will function well in the usual resistor feedback circuit.
The criteria are: CATV types. 1 to 2.5W dissipation capability. Good gain at high current 40-60ma 12V (or slightly higher part) Low noise, sub 2db is adeqate for HF FT greater than 500mhz. One such part I've used is the 2sc3356 or 3357 (or the CEL/Renasis part of the same flavor). There are plenty of choices possible. When using SMT versions, remember the board and its pads are the heat spreader/radiator. So design accoringly, or take reference from the data sheet. Allison 11915
| 2015-11-26 13:56:20
| vasilyivanenko
| Re: Question: What SMT Transistor for Post-Mixer Amp
| Thanks Allison, great suggestion: I too have found that the 2SC3356 works great in that slot -- also I've plied and characterized: NE46134 http://www.mouser.com/ds/2/286/ne46134-607377.pdf 2SC5551A http://www.mouser.com/ds/2/308/2SC5551A-D-103019.pdf Without appropriate collector heat sinking -- for sure, they'll run away and stink up your lab Best! 11916
| 2015-11-27 05:16:24
| i7swx
| Re: Question: What SMT Transistor for Post-Mixer Amp
| Hi Bob,
I have used BFG135, BFG97 and BFG67 for RF amp without any problems. Noise Figure is not reported but for the BFG67 is 1.3dB at 1GHz and 2.2 at 2GHz, so the others should not have too much different NF. As heat sink I have used bronze thick nuts soldered 11919
| 2015-11-27 08:01:32
| John Harding
| Re: Question: What SMT Transistor for Post-Mixer Amp
| Why not look at the Clifton Labs Norton Amp - all surface mount. Earlier versions had thru hole. Happy Holidays | |||||||||||||||||||
