Conversation
jmorris

James Morris

Working on a 10 GHz power amp. #hamradio #amateurradio #electronics #microwave
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jtfletchbot@mastodon.hams.social

Josh KD2YGL

Reply to @jmorris

@jmorris What's the input and output wattage? If you don't mind my asking.

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jmorris

James Morris

Reply to @jtfletchbot@mastodon.hams.social
@jtfletchbot this is for a TGA2623-CP device (yet to arrive), with the aim of 25W out for about 60mW in.
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jmorris

James Morris

Reply to @jmorris
Edited 3 months ago
@jtfletchbot I believe it can produce more linear power with higher voltage and aggressive cooling, but 25W will be a good start.
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jmorris

James Morris

Reply to @jmorris
@jtfletchbot btw, the PCB and housing is from Lothar Baier, https://texasmicrowave.com/ . Saves a mountain of busywork for me.
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jtfletchbot@mastodon.hams.social

Josh KD2YGL

Reply to @jmorris

@jmorris That's very cool! I wish you luck in your endeavors!

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jmorris

James Morris

Reply to @jmorris
Load testing the bias power supply. The amp uses an expensive ($650) GaN transistor which must have bias applied before main power, or it will be destroyed - it’s ‘on’ by default and needs bias to switch ‘off’. I’m being extra careful with this, will also verify the power up sequence on a scope, response to short circuit etc.
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jmorris

James Morris

Reply to @jmorris
Edited 3 months ago
Here's a trace of the power up sequence, with the gate voltage at the top, and drain at the bottom. I'm not sure if the CRO is fast enough to catch the sequence correctly, because I can't tell if there's a gap between gate & drain. IIUC, the negative regulator chip provides a 'voltage ok' signal that is used to switch the gate, so it should be ok. But, I'll keep investigating until I'm sure.

This is the kind of thing that leads to long development times for amateur microwave radio projects, so many (fascinating) rabbit holes and a lot of learning as you go. I wonder if more people knew about this aspect of the hobby, whether we'd see more and younger people joining.
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n8dmt@mastodon.radio

Gary @N8DMT

Reply to @jmorris

@jmorris Analog Devices makes voltage sequencers for turn on and turn off control. Digikey has an overview article to help designers get started. Have found turn-off to be a bigger challenge than turn-on…

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