+5v regulator

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#21
Clear enough, small inductors block RF on the lines.


Just to make the idea of the looped ferrite more clear, this is the way how I did it. Using a 25 Ga. or smaller magnet wire (insulated) I was able to make the loop through the ferrite.
 
#22
Re: Looped beads

apassgear said:
Kuei,

Would the use of the looped ferrite bead provide better RF isolation? Speaking of low load as applied to DACs, say 25/30 mA
Click to expand...

Hi

Looped ferrites have higher capacitance as well. This is sometimes done on purpose to create an LC network with a peaking impedance (> 1 k-ohm) in a certain (small) frequency range

If you look at the Murata site you see plenty examples

I prefer hybrid chokes, one "traditional" choke and one ferrite bead

best regards
 
#23
Ferrite beads become resistive at a certain frequency range, and reactive on either side. You must know the "mix" to determine at what frequencies this holds true for. They are intended for use in this range to attenuate signals without introducing DC loss, as would be the case with a resistor.

Looping the wire increases the loss.......along with the other effects G. Tent mentions.

Jocko
 
#24
Re: Re: +5v regulator

Kuei Yang Wang said:
Koinichiwa,



I found the LT/LM1085-5 (the fixed Voltage Version of the 1085) to be NO improvement on normal 3-pin regs. There is a simple reason too. The build-in resistor divider has not got the option to bypass the ADJ-2-GND resistor, which in such regulators actually drastically lowers noise and output impedance.

Now you could of course use the Adjustable version of the 1085 and incude the two needed resistors and the bypass cap, in which case it would actually be better than any 7805 I have come across, but ONLY then.

My personal preference for a "precision" 3-Terminal regulator circuit is attached. This is suited of course only to relatively low currents, with a suitable CCS (selected J-Fet) it can be used up to past the 50mA output current region.

If you don't mind exceeding the LM334 rated max current (I have done it a few times with no ill effects) you can have more output current even using the LM334, simply stay well within the dissipation rating of the LM334.

The actual regulator is the bit in the Box, the three decoupling Cap's are my recommended local decoupling scheme regardless of regulator used (7805 or the like do need a larger value Os-Con, more like 100uF++ though).

The actual advantage over the usual 3-pin types is usually realised in noise AND much more imporatntly in circuit if the regulators are local to a given chip the Impedance, which remains constant and low up to around 100KHz.

The Os-Con extends this wide range of low PSU impedance to around 500...600KHz. The other SMD caps IF APPLIED WITH MINIMAL LOOP AREAS keep the impedance low past the 30MHz mark...

I find that wiring up this circuit using the two TO-92 cases superglued together and using 1206 SMD resistors makes for a VERY compact circuit that can be fitted instead of most 3-Pin regulators and is not THAT difficult to make.

I also always have ferrite beads on both input to and output from the CCS, this helps to kill feedthrough at higher frequencies. Adding a series inductor somewhere on the board before the trace joins into the main PSU bus is also a good idea. Often the Designer has already thoughtfully (NOT) provided suitable Wirebridges that can be replaced by radial or axial inductors. If not you can often fit an SMD inductor into a PCB Trace.

Of course, this circuit can be bettered but with it's 5-part simplicity, constant current draw and short AC loops it offers much better insulation of PSU lines against each other and noise and that with components that are cheap and easily obtained. It is not a universal Reg but simple and often applicable in modding existing gear.

Anyway, my experiences and thoughs only.

Sayonara
Click to expand...

Goedemorgen/goedemiddag/goedeavond.
Kuei, do you feel the Oscons are better than the Blackgates in this application?
I don't buy the sales talk from Jelmax: paralleling two equal inductors does not cancel them, only halves the value.
I did notice some raving by Linerar Technology about the Oscons in there LT1111 datasheet.
I see the Oscons also in the Trichord3 Clock and the Netaudio Clock. But Audiocom Super Clock II uses Blackgates. And on the Lcaudio site they explain tantalum is the best. It is all very confusing for me:bawling:
Tot ziens,
 
#25
Re: Re: Re: +5v regulator

Elso Kwak said:


Kuei, do you feel the Oscons are better than the Blackgates in this application?
Click to expand...

Well, (almost) every time I use BG's I find my systems sound turns into a direction I don't like.

MAYBE I just cannot wait for them to break in, or maybe I just have always used the wrong the BG's or the BG's reveal all that is wrong with my system or G*d knows what.

But basically, I don't like BG's. I know loads of people like things I don't, such as BG's, Oil Caps, Resistive volume controls, 6SN7 Driver stages and the list goes on, including the TDA1543 (actually, I like the TDA1543, I just like the TDA1541 better...).

My money is on Polyprops, Mylars or Elna Silmic for Audio, Os-Cons and SMD Ceramics for Digital and SOMETIMES BG NX-HiQ for special super low noise circuits (like the secondary PLL in my DAC).

Elso Kwak said:

I see the Oscons also in the Trichord3 Clock and the Netaudio Clock. But Audiocom Super Clock II uses Blackgates. And on the Lcaudio site they explain tantalum is the best. It is all very confusing for me:bawling:
Click to expand...

I have the Audiocom Superclock 1 with a stack of BG's (all NX-HiQ and it is superb, while the Tricord clocks I have tried at best where so-so. I tried BG's again after that experience and still dind't like them much. Tantalum used to be "good" about 20 Years ago, nowadays Os-Con's and related similar solid electrolyte types have the edge by a long stretch. SMD Multilayer Ceramics also are getting serious contenders nowadays.

Sayonara
 
#28
Re: Re: Re: Re: +5v regulator

Kuei Yang Wang said:


Well, (almost) every time I use BG's I find my systems sound turns into a direction I don't like.

------------------------------------------
There is BG, BG-FK, BGN, BGNX and they are not created equal.
For coupling FK and N sound very good after break in. BG-PK doesn't sound special. NX doesn't do it for me in decoupling as uggested by Audiocom. The BG-Cs (cheaper) sounds quite good in coupling too. The Super E configuration is also worth trying and gives a more extended treble.

One cannot generalise and only FKs offer low tan delta comparable to OSCONs. The latter also have variations of the order of 3. For digital circuits, it is worthwhile selecting the best OSCON SGs. For analog use, the right BGs do help to solve problems such as woolly bass, fierce treble, neutered mid etc.

There is no bible.
Click to expand...
 
#29
and negative regulators?

How about similar high quality negatibe regulators? There is the LT1185, which is a 5 pin precision adjustable negative regulator. I am wondering what other high quality negative regulators are out there.
 
#30
Re: and negative regulators?

Koinichiwa,

gilid said:
How about similar high quality negatibe regulators?
Click to expand...

I thought that was obvious....

Sayonara
 

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#32
Re: regarding the LM431 regulator

Koinichiwa,

yves said:
Are there stability problems with increasing the
15u oscon value to 100u or 470u?
What about a large (say, 47u) cap at the 1k at
the adj node of the 431?
Click to expand...

Yes, both can be done. BTW, the 47uF Cap needs to go from Adj to positive side of the reg, not the negative side as it would be for 3-Pin adjustable.

The reason for the specified Os-Con and the omiting the bypass is to match the various (parasitic) resistances to avoid nasty resonances. All Cap's have broadly the same ESR and the Reg has a similar internal impedance.

Sayonara
 
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