Re: Regulators
Hi
tens of m-ohms. Availble versions will be +3.3, +5.0, and +/- 15V
best
PHEONIX said:
Hi
tens of m-ohms. Availble versions will be +3.3, +5.0, and +/- 15V
best
Regs
Hello Guido
So they will be fixed voltage ouput types of regulators. How low in noise will they be.
What will be a typical PSRR be and will this be across the 500Khz .
Regards
Arthur
Hello Guido
So they will be fixed voltage ouput types of regulators. How low in noise will they be.
What will be a typical PSRR be and will this be across the 500Khz .
Regards
Arthur
Re: Regs
Hi Arthur
tens of nV/SqrrtHz
I try to achieve >80dB, but still have to measure that
best
PHEONIX said:
Hi Arthur
tens of nV/SqrrtHz
I try to achieve >80dB, but still have to measure that
best
Regulators
Hello Guido
If you had a PSRR of >80db it would be fair to say you have >80 of open loop gain in you reg circuit . Lets say your ref is 1.6 Volts and you multiply this by 2 to get roughly 3.3 V with a drain current of 100 mA (using bipolars) you should have output impedence in vicinity of milliohms region and not tens of m-ohms.
Is there something I am not getting here , I think your ouput imepedence is too high for the amount of gain you have or are my assumptions wrong about the open loop gain you have in your circuits.
Regards
Arthur
Hello Guido
If you had a PSRR of >80db it would be fair to say you have >80 of open loop gain in you reg circuit . Lets say your ref is 1.6 Volts and you multiply this by 2 to get roughly 3.3 V with a drain current of 100 mA (using bipolars) you should have output impedence in vicinity of milliohms region and not tens of m-ohms.
Is there something I am not getting here , I think your ouput imepedence is too high for the amount of gain you have or are my assumptions wrong about the open loop gain you have in your circuits.
Regards
Arthur
Re: Regulators
Hi Arthur
Or maybe I throw away some gain here and there
back to work now
PHEONIX said:
Hi Arthur
Or maybe I throw away some gain here and there
back to work now
Re: Re: Regulators
Guido,
Just to be sure, do you mean 10's of mOhms (like 20 mOhms) or tenths of mOhm (like in 1/20 mOhms) ?
Jan Didden
Guido Tent said:
Guido,
Just to be sure, do you mean 10's of mOhms (like 20 mOhms) or tenths of mOhm (like in 1/20 mOhms) ?
Jan Didden
measuring a regulator's impedance and stability:
this article appeared in EDN -- a great way to impedance, stability and whether or not the regulator is going to oscillate is to use a CFB opamp inserted in the feedback loop -- saves the expense (very) of a wide-band transformer:
http://www.tech-diy.com/loopstability.pdf
this article appeared in EDN -- a great way to impedance, stability and whether or not the regulator is going to oscillate is to use a CFB opamp inserted in the feedback loop -- saves the expense (very) of a wide-band transformer:
http://www.tech-diy.com/loopstability.pdf
jackinnj said:
The issue of measuring Zout is not trivial, for several reasons. You really have to measure at the feedback pick-off point to get real performance. Measuring half an inch further on the wire will easily raise Zout (as measured) 10 or 100 times.
I have measured Zout on my own designs below 1 milliOhms over the audio band, but then again there is no way you can realise that in a complete design unless you do remote sensing and pick off the feedback at the load point, for instance at the opamp supply pin close to the package. (I mean the opamp to-be-powered or another audio circuit to be powered). Such is the law of diminishing returns.
Jan Didden
not all 7805 are that bad...
hi,
i had measured the noise voltage at the output of various 7805 regulator ic's with light load and only 10uF electrolytic-cap. the ac voltage at the output has been amplified with 40db. i used a simple dvm, so its more a 'hint' then a precise measurement...
MC7805C (Korea) 1.2mV
L7805CV (SGS) 0.4mV
L7805CV (ST) 1.3mV
SD7805D 1.0mV
MC7805CT (M) 0.4mV
JRC7805A 2.2mV
JRC78M05A 2.3mV
L78S05CV (ST) 1.5mV
comparing:
LM317T (M) @5V 1.7mV
LM317T (ST)@5V 1.4mV
LT1086CT-5 (LT) 6.1mV
L7808CV (SGS) 3.1mV
L7812CV (ST) 4.6mV
references:
TL431C (ST) 0.9mV
LM336Z-5.0 2.3mV
LM336Z-2.5 (LT) 0.8mV
LM336 (ST) 0.6mV
ZPD 5.6V (zener diode) 0.0mV
ZPD 3.3V (zener diode) 0.0mV
hi,
i had measured the noise voltage at the output of various 7805 regulator ic's with light load and only 10uF electrolytic-cap. the ac voltage at the output has been amplified with 40db. i used a simple dvm, so its more a 'hint' then a precise measurement...
MC7805C (Korea) 1.2mV
L7805CV (SGS) 0.4mV
L7805CV (ST) 1.3mV
SD7805D 1.0mV
MC7805CT (M) 0.4mV
JRC7805A 2.2mV
JRC78M05A 2.3mV
L78S05CV (ST) 1.5mV
comparing:
LM317T (M) @5V 1.7mV
LM317T (ST)@5V 1.4mV
LT1086CT-5 (LT) 6.1mV
L7808CV (SGS) 3.1mV
L7812CV (ST) 4.6mV
references:
TL431C (ST) 0.9mV
LM336Z-5.0 2.3mV
LM336Z-2.5 (LT) 0.8mV
LM336 (ST) 0.6mV
ZPD 5.6V (zener diode) 0.0mV
ZPD 3.3V (zener diode) 0.0mV
Re: not all 7805 are that bad...
Zeners are considered one of the noisiest parts around to make supplies, so maybe there's something wrong on the way you are doing these measurements.
Carlos
Reina said:
Zeners are considered one of the noisiest parts around to make supplies, so maybe there's something wrong on the way you are doing these measurements.
Carlos
>Zeners are considered one of the noisiest parts
i found the results surprising, too. the current through the zeners was several mA. the values are correct. the noise amplifier was my hifi-amp and my ears says the same. zener noise is important at low currents in amplifier circuits, of course. it is much higher than the noise from a diode (transistor) but nothing in compare to voltage references, you see.
i found the results surprising, too. the current through the zeners was several mA. the values are correct. the noise amplifier was my hifi-amp and my ears says the same. zener noise is important at low currents in amplifier circuits, of course. it is much higher than the noise from a diode (transistor) but nothing in compare to voltage references, you see.
Re: Re: not all 7805 are that bad...
All zeners are noisy, but som zeners are noisier than others. 🙂
I don't know if you remember, or even read, about the experiments I did about a year ago (www.diyaudio.com/forums/showthread.php?postid=417008#post417008).
According to my measurements there is a very big difference in zeners depending on their voltage drop. The noisiest ones seem to be those having a voltage drop close to the shift from zener breakdown to avalanche breakdown. These are better avoided if noise is of any concern at all. However, those zener diodes that have a sufficiently low or high voltage have quite respectable noise values. Also, don't forget that ultimately the noise should be correlated with the voltage. The 12 V zeners I measured had about the same noise voltage as LEDs. Then bear in mind that it would take a string of LEDs to achieve a 12 V drop, so for high voltage drops it seems that zeners are to be preferred.
It should also be noted that for many of the devices I tested, the noise varies enormeously with the current, while for others, the current hardly matters.
Finally, I only tested components that basically work as shunt regulators (diodes, LEDs, zeners, TL431 etc.). If measuring series regulators like 78xx and 317, one would have to come up with some test setup that gives a fair comparison. Probably (but I never measured them) series regulators will have a noise that depends on the output current. That is, for a fair comparison between shunt and series regulators, we must also consider the load. I only studied the case of no load, that is, shunt regulators used as voltage references. A series regulator, however, typically desires some minimum load to function properly, so even if it is to be used only as a voltage reference, it might need som suitable load to achieve its best noise behaviour.
carlmart said:
All zeners are noisy, but som zeners are noisier than others. 🙂
I don't know if you remember, or even read, about the experiments I did about a year ago (www.diyaudio.com/forums/showthread.php?postid=417008#post417008).
According to my measurements there is a very big difference in zeners depending on their voltage drop. The noisiest ones seem to be those having a voltage drop close to the shift from zener breakdown to avalanche breakdown. These are better avoided if noise is of any concern at all. However, those zener diodes that have a sufficiently low or high voltage have quite respectable noise values. Also, don't forget that ultimately the noise should be correlated with the voltage. The 12 V zeners I measured had about the same noise voltage as LEDs. Then bear in mind that it would take a string of LEDs to achieve a 12 V drop, so for high voltage drops it seems that zeners are to be preferred.
It should also be noted that for many of the devices I tested, the noise varies enormeously with the current, while for others, the current hardly matters.
Finally, I only tested components that basically work as shunt regulators (diodes, LEDs, zeners, TL431 etc.). If measuring series regulators like 78xx and 317, one would have to come up with some test setup that gives a fair comparison. Probably (but I never measured them) series regulators will have a noise that depends on the output current. That is, for a fair comparison between shunt and series regulators, we must also consider the load. I only studied the case of no load, that is, shunt regulators used as voltage references. A series regulator, however, typically desires some minimum load to function properly, so even if it is to be used only as a voltage reference, it might need som suitable load to achieve its best noise behaviour.
it's helpful to bandwidth limit the noise measurements -- for references it's typically in a range of 10 milliHz to 10 Hz, for supplies, 10Hz to 100kHz. You get more repeatable results if you isolate the DUT in its own shielded environment and take care to make sure that your cabling to the test instrument remains unmoved.
further, the noise measurement is integrated over time -- take a look at Texas Instruments product folder for the TL431.
just like paralleling JFETs -- when you parallel shunt references the noise drops -- but there is a point of optimality which I found to be 3 LM329's for the super-reg.
fwiw -- here's a picture of the noise on a regulator for a tube preamp -- I previously posted it in the Tube Threads -- it's a variant of the "WJ Pooge" which appeared in Audio Amateur in 1979 for low voltage applications and was scaled up by Walt for the Marantz 7C and Dynaco PAS in 1982 -- the noise appears to be about 5 mV or so 16ppm. The top line is the noise from a Heath IP-17 tube-type regulated supply.
further, the noise measurement is integrated over time -- take a look at Texas Instruments product folder for the TL431.
just like paralleling JFETs -- when you parallel shunt references the noise drops -- but there is a point of optimality which I found to be 3 LM329's for the super-reg.
fwiw -- here's a picture of the noise on a regulator for a tube preamp -- I previously posted it in the Tube Threads -- it's a variant of the "WJ Pooge" which appeared in Audio Amateur in 1979 for low voltage applications and was scaled up by Walt for the Marantz 7C and Dynaco PAS in 1982 -- the noise appears to be about 5 mV or so 16ppm. The top line is the noise from a Heath IP-17 tube-type regulated supply.
An externally hosted image should be here but it was not working when we last tested it.
jackinnj said:
Hi
If we want 2 single noise figures, that is a good proposal. Not everyone has a spectrum analyser at his or her lab.
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