Mmini regulator (sample offering)

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#223
Hello Coffin, I'm new to the forum and just spotted this thread. I would love to try one of the 5-30V dual boards and a positive 5-30V if any left. If not, please put me on the list to buy when they start selling.

I actually have a full dual rail Jung SR - style regulator breadboarded and working here (but no PC board) that I made for a LME49710/LME49600 headphone amp project. I made it using LME49710s (metal can to-99 version) for the regulator op amp and they work great - and I see LM49710's on your BOM for the board. I can just pull several of the parts off my breadboard and solder them right into the board. 🙂

Congratulations to your friend on the design. I'm an EE, athough I'm wayyy out of date, and I've been stewing over design improvements on this thing for a few weeks now. I like your friend's transistor buffer on the level-shifter on the output of the op amp. I wanted to do something similar but hadn't come up with a workable design yet. I had used (another) LM329 in mine instead of the zener just because I could - it worked out perfectly with a 9V output. The LME49710 output hovers around 2.5v. That op amp is happy to within about 1.5v to the rails for the given (light) load.

That differential design for the current source is really interesting. I've measured voltages on all points on mine with loads of 40mA, 250mA, and 450mA, and with input voltages (from dual wall warts) of 12 and 24 (actually up to 14.5 and 24 with those things on light load). The current source feeding the pass transistor and zener definitely seems like the weak point on stability. I read through Jung's original articles the last few days and see he acknowledges that in the 2000 print. I've been trying to think up something more stable then the green led. At least I have it biased about mid way in the most-linear range after studying the datasheet graphs. Your friend's design should eliminate any added (to the LED instability) base-emitter variation on that source transistor.

Now I'm working on coming up with a design to replace the SR "pre-regulator" with a gyrator in the middle of a butterworth filter. 🙂 Just found something similar a person had posted a few years ago. I would love to see that kind of thing added to the board. The pre-reg appararently helps stabilize that current source. If the design is clever enough there may be a way to make the one transistor be both a pre-reg (feed it with a voltage reference - zener) and a gyrator. Then it could both fix a voltage across the reg pass trans and that current source *and* work as an active butterworth LP filter. Or something like that. 🙂

Thanks!
-agdr
 
#225
2SC3519 pass transistor

Hi Coffin

Can I use a smaller pass transistor, something like a BD139 if I don't require such a high current? I realise the pin outs are different but is the 3519 pass transistor just there for its 15A capability?

thanks

Rob
 
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