Digital app's
Well, since most digital apps are 5V or lower, the AD825 and AD797 are excluded for that reason.
I've not used many reg's for digital stuff, so my experience is more limited here, but certainly there are some newer, low voltage, op-amps worthy of investigation, as an alternative to the AD817, try looking to some of the THS series from TI. Most of the newer AD parts that are recommended for other apps (e.g. AD8065) are also unsuitable for a 5V reg, due to the common mode input range limitations of the FET part of the front end.
They may work with a lower reference voltage than the 2.5V I spec as standard for a 5V reg?
I'd recommend starting with the AD817 as a reference, then moving from there; many of the alternatives may not be as quiet either, since the high speed parts have much higher noise corners than some of the noisier looking alternatives, which may be important in some app's.
The AD8021 looks interesting, for example, but has a high noise corner and would almost definitely need additional compensation to work.
Andy.
Well, since most digital apps are 5V or lower, the AD825 and AD797 are excluded for that reason.
I've not used many reg's for digital stuff, so my experience is more limited here, but certainly there are some newer, low voltage, op-amps worthy of investigation, as an alternative to the AD817, try looking to some of the THS series from TI. Most of the newer AD parts that are recommended for other apps (e.g. AD8065) are also unsuitable for a 5V reg, due to the common mode input range limitations of the FET part of the front end.
They may work with a lower reference voltage than the 2.5V I spec as standard for a 5V reg?
I'd recommend starting with the AD817 as a reference, then moving from there; many of the alternatives may not be as quiet either, since the high speed parts have much higher noise corners than some of the noisier looking alternatives, which may be important in some app's.
The AD8021 looks interesting, for example, but has a high noise corner and would almost definitely need additional compensation to work.
Andy.
Marks package with PCB's for European/Asian region
arrived yesterday.
I intend to start sending out the packages tuesday. I normaly have my free day on wednesday, however the next week I won't so I'll have to see when I can visit the post-office.
Henk
arrived yesterday.
I intend to start sending out the packages tuesday. I normaly have my free day on wednesday, however the next week I won't so I'll have to see when I can visit the post-office.
Henk
Re: Digital app's
Hi Andy,
The AD829 has low noise and has the speed of the AD817. But I would not power the opamp from the digital regulated +5V supply for obvious reasons:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=34795&perpage=15&pagenumber=1
😉
ALW said:
Hi Andy,
The AD829 has low noise and has the speed of the AD817. But I would not power the opamp from the digital regulated +5V supply for obvious reasons:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=34795&perpage=15&pagenumber=1
😉
Coulomb said:
Board only orders are ready to ship on Monday.
Orders with caps, I need to find adequate packaging.
Regards
Anthony
Please read the data sheets!
The AD829 is not unity gain stable, or specced for anywhere near 5V operation, so it won't work (without some work).
Andy.
The AD829 is not unity gain stable, or specced for anywhere near 5V operation, so it won't work (without some work).
Andy.
Delivery Update
I found some Padded mailers perfect for the job at work, better they are free!!
All but three orders are ready to go on Monday.
Regards
Anthony
Coulomb said:
I found some Padded mailers perfect for the job at work, better they are free!!
All but three orders are ready to go on Monday.
Regards
Anthony
Re: Please read the data sheets!
Hi,
As I said I would not power the opamp from 5V but something near 10V.
I just read the datasheet and it claims "Specified for +/- 5V to +/- 15V operation". Also the datasheet gives custom compensation making it possible to use the part as a unity gain follower or inverter. But a gain of two would be possible with a 2.5V reference.
Now who does not read the datasheet...............?
🙄
ALW said:
Hi,
As I said I would not power the opamp from 5V but something near 10V.
I just read the datasheet and it claims "Specified for +/- 5V to +/- 15V operation". Also the datasheet gives custom compensation making it possible to use the part as a unity gain follower or inverter. But a gain of two would be possible with a 2.5V reference.
Now who does not read the datasheet...............?
🙄
Elso,
I knew that!
I posted in reply to fmak, who seemed to be considering the AD829, without any sanity checking whatsoever.
As I said, it will not work, without some work, you've nicely re-iterated that - thanks 😉
Andy.
P.S. Why wouldn't you run the op-amp from the reg o/p (beyond the supply limitation problems)?
I knew that!
I posted in reply to fmak, who seemed to be considering the AD829, without any sanity checking whatsoever.
As I said, it will not work, without some work, you've nicely re-iterated that - thanks 😉
Andy.
P.S. Why wouldn't you run the op-amp from the reg o/p (beyond the supply limitation problems)?
They'll enter it anyway, unless you deal with them, since they will be present on the supply feed to the clock, which comes from the reg o/p, which in turn is where the feedback connects to...
That can all be dealt with by optimising decoupling, I'd have thought, plenty of clues in other threads for that.
Here wouldn't be a bad place to start: -
http://www.diyaudio.com/forums/showthread.php?threadid=29259
Andy.
Clock Spikes
Hi Andy,
Yes you are right.
Besides that I tried that approach for a analog supply i.e. using the output as supply for the opamp, and it did not give any audible improvement.
For a supply for a clock circuit I don't believe any feedback from the output is good. Well that rules out the opamp..... Back to Jocko's follower?😉
The thread you advised a good place to start? It was one of the most confusing threads I ever participated in......
Hi Andy,
Yes you are right.
Besides that I tried that approach for a analog supply i.e. using the output as supply for the opamp, and it did not give any audible improvement.
For a supply for a clock circuit I don't believe any feedback from the output is good. Well that rules out the opamp..... Back to Jocko's follower?😉
The thread you advised a good place to start? It was one of the most confusing threads I ever participated in......
Feedback and stuff
For all feedback amps (regs / audio / anything) you need to be careful of the bandwidth of the signals you feed into it, via any of the inputs.
That's what good design is about, and why many people find non-feedback systems easier to get working at their best. Open loop systems may in some circumstances be the best solution of all, there's plenty of examples out there.
Andy.
For all feedback amps (regs / audio / anything) you need to be careful of the bandwidth of the signals you feed into it, via any of the inputs.
That's what good design is about, and why many people find non-feedback systems easier to get working at their best. Open loop systems may in some circumstances be the best solution of all, there's plenty of examples out there.
Andy.
Lowering the Noise Floor
But certain contributions were worth reading; Guido, Jocko some bloke called Elso 🙂
Andy.
But certain contributions were worth reading; Guido, Jocko some bloke called Elso 🙂
Andy.
ALW said:Elso,
I knew that!
I posted in reply to fmak, who seemed to be considering the AD829, without any sanity checking whatsoever.
-------------------------------------------------------------------------------
I didn't even know about the AD829. Who is not reading the posts?
Re: Clock Spikes
I shall soon settle this, by powering a Tent or Valpey Fisher clock with the 5V version, and measuring then listening to the combied units.
The Audiocom 5V regulator totally collapse when feeding 30mA or so to a XO; even though it is excellent with a resistor!
Spews out harmonics like a sick man; clearly not stable.
-------------------------------------------------------------------------------Elso Kwak said:
I shall soon settle this, by powering a Tent or Valpey Fisher clock with the 5V version, and measuring then listening to the combied units.
The Audiocom 5V regulator totally collapse when feeding 30mA or so to a XO; even though it is excellent with a resistor!
Spews out harmonics like a sick man; clearly not stable.
Re: Clock Spikes
Hi Andy,
Actually I meant entering the powersupply pin(s) of the opamp. But feedback taken from the output would also be bad. There is a way around with a follower after the opamp and the feedback taken from the base of the transistor. This will of course make load regulation worse but I don't see that as a problem for a supply for a clock circuit.
😎
Elso Kwak said:
Hi Andy,
Clock spikes would enter the feedback loop.
Hi Andy,
Actually I meant entering the powersupply pin(s) of the opamp. But feedback taken from the output would also be bad. There is a way around with a follower after the opamp and the feedback taken from the base of the transistor. This will of course make load regulation worse but I don't see that as a problem for a supply for a clock circuit.
😎
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