The simplistic Salas low voltage shunt regulator

[pidesd]

yet another interesting part?

found this one http://diodes.com/datasheets/DMN3730U.pdf


negatives: max 30V Vds and sot-23....

positives: 70 pF ciss and maybe high Yfs at low Id

and here is a similar one in P channel...

http://diodes.com/datasheets/DMP31D0U.pdf

 

[Salas]

Good part. Enhancement mode.

 

[Nosian]

any News from pcb front?

or the final scheme & values for 5V dac-reg? (sorry but I wish I were able to read the threads)
thanks in advance

 

[Ryssen]

Is there any nois messaurement on the salas shunt?

 

[Salas]

http://www.linearaudio.net/images/letters.pdf/V4 JW F7.pdf

 

[Ryssen]

Thanks!

 

[Ryssen]

I have a pcb with salas shunt V1.0 and I need 3,3v out.now the lowest I can get is 3,55v so instead of changing to BJT at the output can I use a 1N4007 in series with the possitive to lower the output 0,7v.
Is there any dissadvantage of doing this??

 

[Salas]

The diode's dynamic impedance comes in the picture.

 

[Ryssen]

So I change to BJT then,the funny thing is that I have another pcb exactly the same and it can go to 3,3v or even lower,it must be the component tolerance then?

Edit:Could you explais about the Dynamic impedance

 

[Salas]

Its the VGS tolerance mainly. There is a delta ohm regarding the steepness of a diode's curve, that will add to Zo and modulate with the load's current draw dynamic.

 

[AndrewT]

I have a pcb with salas shunt V1.0 and I need 3,3v out.now the lowest I can get is 3,55v so instead of changing to BJT at the output can I use a 1N4007 in series with the possitive to lower the output 0,7v.
Is there any dissadvantage of doing this??

An lm317 with a LED in the adj lead gets close to 3v3.
Just select 317 & LED to achieve as close as you need.

 

[Ryssen]

An MJE350 is fitted,and it´s now giving 3,3v..

 

[Salas]

Yes, BJT leaves it a good margin for Vbe VS VGS.

 

[pidesd]

hi all,

maybe some you remember a discussion concerning semiconductor reliability relative to operating temperature

i sent e-mail to a few manufacturers for j111 jfet and fairchild responded to me with the attached.

maybe there is a chance it may contribute to the subject.

this link may also help to understand

http://www.hp.woodshot.com/hprfhelp/4_downld/products/xrs/at41511_r.pdf

 

[Salas]

Interesting, thanx.

 

[pidesd]

BTW salas,

have you played with bsp129?

i built a b1 buffer and have no means to measure anything

but my ears tells me that it sounds fabulous in signature but maybe it is noisy...?

EDIT: buffer is between sound card and f4 ''sans'' jfet. BTW i did not compared it yet to complementary k170/j74....

also, f4 drives directly lowther pm6c or Axiom bookshelves without voltage gain stage

 

[Salas]

I will, I have it in mind, but I was doing other stuff, some pro speaker protos for bars and clubs. I expect them noisier than JFETs, that is for sure, also some degeneration resistors to keep them from drifting. Did they prove necessary in yours?

 

[pidesd]

degen source resistor i did put.

did not tried without them but played with values from 10 to 2.5(used what i had)

but some russian guy on the web already built a commercial version( i think) for headphones with 1 ohm res.

also, sharing heatsink has fantastic tracking(used thermal paste)

 

[Salas]

He must have read my BS170 crack a couple of yrs ago.😀

 

[pidesd]

currently running 2W each, heatsunk on one face only and it looks like temperature is OK...looks like🙂