Den tirsdag den 8. december 2015 kl. 01.33.55 UTC+1 skrev John Fields:
or
ole
mThink
out
he PNP
ldn't
ld be
got
ut
ou
t can
ust
Ke voltage is usually 240R, 1.25V/240R ~= 5mA
ed to
you must really spend a lot of effort trying to come up with twisted ways that everything John says is somehow bad
-Lasse
Not everything Larkin says is bad, but when it is and it's twisted to make it seem good, it deserves to be looked at through a Rochelle salt crystal.
John Fields
Well I want to see where the R's and C's are. I've done thing's like that, with lm317/337.
But I agree at the moment who knows. I hooked up "that" circuit w/o ground today....
48V DC in.. the output was railing the scope, (x1, ~50 Vp-p.) Oops.Hmm. OK I better post the whole thing (there's not much) here tomorrow, certainly a "beer"* for every addition component I end up adding.
George H.
*I don't know how to pay off all the "beers" I owe to SED, except to pay it forwards as always.
I wouldn't say bad. But much of what he posts here is a bit stupid. He implies that XO's and huge FPGA's are the universal loads. What???
-- Rick
e
hink
ut
PNP
n't
be
tcan
tvoltage is usually 240R, 1.25V/240R ~= 5mA
to
Geesh John F., I don't feel that way at all. I think JL is confused (polite, euphemism for wrong) about some things, but it's not a big deal to me. I mean there's some chance I'm wrong instead. Say 10%, whatever. (50%, if it's important to you, you spend time and become expert.) And 90% of his output I find stimulating... (circuit/ science/ life wise...)
George H.
The subject was minimum load and adjust pin currents of regulators. The load is relevant.
I do lay out a modest board now and then, but it takes weeks to lay out a serious multilayer BGA-studded board, so I have people who do that for me.
I did this, schematic and layout, in a weekend, which is about my attention span for a layout.
But no BGAs. I don't recall ever routing a BGA, or touting my ability to do so. I certainly could; there's nothing special about BGAs except that they tend to have a lot of connections.
I sometimes lay out breadboard sorts of PCBs, to test circuit ideas. It's not practical to breadboard some things any other way.
When I do one of these, I walk around and see if anybody else might want me to throw in a test circuit for them. When the boards come in, I shear them up and hand out the pieces.
You just don't like me, so you irrationally whine about anything that I do. That includes making suggestions to improve your circuits.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
But most of it is good. I rarely post the bad stuff, unless it's especially interesting.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Those are the key elements. The reservoir caps handle load current imbalance in the very short term, leaving zeners to take care of all remaining imbalance. Enough gotchas to make many uncomfortable, but it does work.
NT
in:
tor
hole
rom
. Think
nt out
the PNP
ouldn't
ould be
e got
but
you
it can
,djust
10Kthe voltage is usually 240R, 1.25V/240R ~= 5mA
at
eep
igned to
ys
well it started with him mentioning using two stacked regulators to get
1.25V and 2.5V for core and IO on an FPGA with out resistors. With a huge FPGA is is probably safe to say that minimum load is not going to be an iss ue-Lasse
Seems to me that would only affect opinions that were polarized in the first place. ;-)
--sp
-- Best regards, Spehro Pefhany Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8 Microchip link for 2015 Masters in Phoenix: http://tinyurl.com/l7g2k48
I'd be more inclined to rail-split with an op amp and a couple of BJTs for a class-B buffer, like an LM324 on steroids. ;)
Probably more expensive than your approach though.
It would sure be nice if the TCA0372 came in a proper power package--it's a perfect rail splitter except that it runs really warm.
Audio power amps sometimes use a fun rail-balancing trick--you take an inductor with one end at ground, and switch the other end alternately to V_CC and V_EE. Any imbalance makes DC flow in the inductor to null it out, without a lot of loss.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Can you hang reservoir caps on the output of that? If not the whole thing consumes upto twice the power, depending on the current imbalance.
NT
Sure. You just have to pay attention to the frequency compensation.
Plus you can put the rail splitter ahead of the regulators.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I saw a switching rail splitter somewhere once. It was just an inductor switched alternately between the rails, to common.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I mentioned that just upthread. It's a cool idea.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
As per my experience 7815 will not work if you connect the 9V input to it.
The input must be more than 15V. But you can make it 18V by putting the positive output from the output of transformer.
Your other setup is good but look for this. Share your setup schematic here if you can.
--------------------------------------- Posted through
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.