Just wonder if anybody used the ST series of 7805, esp the precision 1A type L7805AC where the spec states 10uV from 10hz to 100khz, plus low output impendance of 0.017ohm. This is much better than even the lt317, lt1085.
It would be great if this is true as I can use it as I can use it as a simple drop in.
I will have to find it first however.
It would be great if this is true as I can use it as I can use it as a simple drop in.
I will have to find it first however.
Ops, forgot to paste the link to the datasheet.
http://www.st.com/stonline/products/literature/ds/2144/l7805ac.pdf
http://www.st.com/stonline/products/literature/ds/2144/l7805ac.pdf
ChuckT said:
Assumed noise is flat, that would give 158 nV/SqrrtHz
Usually (!) some LF nose is still present beuound 10 Hz so I'd expect more LF noise and some 100 nV/SqrrtHz.
78/79 regs are extremely non linear in output impedance behaviour, avoid them, they act as mixers.
best
Guido Tent said:
Guido,
If I want to avoid 317-type regs to limit the number of components, what 3-pin regs would you recommend for +/- 15V applications? If any 😉 ..
Jan Didden
janneman said:
Hi Jan
Well, yes, if any....
In that range, the LT1086 would be nice, but that one hasn't got a counterpart which thus calls for 2 floating supplies tied together.
There is a number of tricks to make such 3 pin regs sound better. One of them is loading them such that their output stage delivers more current (hence becomes more linear). Still, they were never designed with audio in mind.
Currently, Tentlabs is designing a discrete regulator that subsitutes 78/79 style regs. Keep watching the webspace......
best
Hi Guido and Jan!
Are your regulators a drop-in? Just pull the 7xxx out and the discrete in?
Cheers
Tom
Are your regulators a drop-in? Just pull the 7xxx out and the discrete in?
Cheers
Tom
Thanks for the info.
I'll just use the 780* as pre-regulator only then, and a lt317 or lt1021 after for digital use.
For the LT1021, does anybody know if the output current is enough for a 74hc chip or an ocillator? Or do I need to add a 2n2905 to boost the current?
If not, then this is as simple to use as the 7805 but with better specs.
I'll just use the 780* as pre-regulator only then, and a lt317 or lt1021 after for digital use.
For the LT1021, does anybody know if the output current is enough for a 74hc chip or an ocillator? Or do I need to add a 2n2905 to boost the current?
If not, then this is as simple to use as the 7805 but with better specs.
The LT1021 will sink 10mA.
If you are willing to try SMT, try the LT1763 (+) and LT1964 (-) Low Noise regulators.
And of course, using an LM317 as a current source to drive a very low noise regulator is the ultimate option (as demonstrated in the last of the SuperReg articles in 2000) . Don't forget that these devices are available in TO-92 for < 100mA applications.
If you are willing to try SMT, try the LT1763 (+) and LT1964 (-) Low Noise regulators.
And of course, using an LM317 as a current source to drive a very low noise regulator is the ultimate option (as demonstrated in the last of the SuperReg articles in 2000) . Don't forget that these devices are available in TO-92 for < 100mA applications.
Guido Tent said:
Hi Guido
When will they be available??
Also, KYW likes LM2937/LM2940 and LM2990 as replacements for 78xx and 79xx. Any thoughts on those?
Arcamaniac said:
Hi Guido
When will they be available??
Also, KYW likes LM2937/LM2940 and LM2990 as replacements for 78xx and 79xx. Any thoughts on those?
Hi,
That would be some weeks from now. Most series regulators have non linear output impedance hence add distortions on the supply rails.
A simple measurement is to inject current into the output (say 10mA. 1kHz), and measure (FFT) the resulting voltage. You may be amazed 😀
best
Regulators
Hello Guido
Will your regulators be configurable in shunt mode operation also.
Will they need a cap on the output to operate.
What will be the open loop bandwidth of the stage.
When you take about inject 10ma @1Khz into the output , do you mean Vout of the regulator, what circuit do you use to apply this stimulus.
Regards
Arthur
Hello Guido
Will your regulators be configurable in shunt mode operation also.
Will they need a cap on the output to operate.
What will be the open loop bandwidth of the stage.
When you take about inject 10ma @1Khz into the output , do you mean Vout of the regulator, what circuit do you use to apply this stimulus.
Regards
Arthur
Re: Regulators
Hi Arthur
Lots of questions, won't answer them all (yet)
no cap required
BW>500kHz
I use a normal signal generator, with 1 k-ohm series resistance. Obviously Vout is of interest !
best
PHEONIX said:
Hi Arthur
Lots of questions, won't answer them all (yet)
no cap required
BW>500kHz
I use a normal signal generator, with 1 k-ohm series resistance. Obviously Vout is of interest !
best
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