He has a strong Aussie accent, a bit hard to understand. It’s a 28 min. YouTube video. He says BD139s have a fT of 250 MHz, but the datasheet I have does not specify any fT because the D in BD139 means they are a low frequency device, not meant for VHFs or RFs in
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Long article https://sites.google.com/site/transistorhistory/Home/us-semiconductor-manufacturers/raytheon-part-one-2 A comprehensive history of the Raytheon corporation. Also information about other companies.
Have you got a USB disk drive or flash drive that was sold at a price so low it was “too good to be true”? Steve Gibson’s Validrive will do spot checks to see if the SSD or flash drive is really what it claims to be. Fake drives are sold for cheap and the
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Me and my high school friend made a DC to DC converter that would give us 30 or so volts at a couple amps from a 12 volt battery. We used germanium power transistors which could not go much above 10 kHz. The Delco’s and the 2N458A’s were our favorites – we managed to push
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Q: What was the first commercially successful semiconductor device? Hint: It wasn’t germanium. https://en.m.wikipedia.org/wiki/Henry_Harrison_Chase_Dunwoody
I made one of these back in 1970 or so. It was inside of a coffee can using the lid for the speaker. This class A power LED driver works good for making a speaker from an audio output transformer and any sheet of steel, even a coffee can with a steel cover. Strip the
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A year or so ago I bought a few 1W mono amplifiers from a Chinese eBay seller for cheap – see the attached photos. The only marking on the PC board is YX-1667 but I’m not sure if that’s the potentiometer or the PC board itself. . I found that if I pushed the 3.5mm
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From FB group Building Transistor Radios 2018-08-24 – The discussion was about the OTL complementary symmetry audio amplifier that Mr. Barnett has posted several times to the group, which uses a 2N3904 and 2N3906. Willie Barnett Let’s talk about current. Suppose your amp has a 9V supply. When the output transistor is turned fully on,
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