UCD separate opamp supply?

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#121
UcD Dilema

Hi Guys,

Sorry to disturbing this topic, I get a dilema here, I want to try these UcD modules, but unfortunately it 's not so cheap like tripath, so Is there a way to do a audition around Houston Texas before I bye .

Thanks,

Alex. 😀
 
#123
I think you can use the same CRD for any, the pad on the board is for a smd like the SST511, you need to know which transistor in the op-amp to bias, with the AD8620 it goes from output to -15v to remove the crap off its supply rail
I'm probably wrong😀 maybe somebody else can confirm
 
#126
maxlorenz said:
I have a question regarding bias mod, 'cause I'm tempted to try it.

J511 is only good for AD8620, wright?
In that case, can someone point me to suitable CDR and/or Jfet to mod the 5532 and BurrBrown 2134 opamps?

It is not that I'm lazy but honestly I don't feel capable of calculating bias current :angel:

Gratefully yours...
Mauricio
Click to expand...


Mauricio,

current source to the negative rail will work with most any op amp, and best I suspect too. 5532 and I think the 2134 too.
The reason is NPN's are usually better than PNP's, so you want to bias the NPN output transistor on, which in most hi fi op amps (Not rail to rail output) this is the one connected to the top rail.

I haven't looked up this CRD, but Its likely fine for most. Tweaking the current would be a nice feature, and likely have some benfit.

Anyone know who makes the CRD discussed so I can look it up?

Also, just a genral comment, and maybe Jan-peter could pipe in, is there any reason at all to force this seperate supply to the amp board. That is to say, can't you just do the whole op amp diff amp input and the supply, like several if need be, on a different board. Wouldn't that be more ideal?

Regards,

Mike
 
#127
Portlandmike said:



Mauricio,

current source to the negative rail will work with most any op amp, and best I suspect too. 5532 and I think the 2134 too.
The reason is NPN's are usually better than PNP's, so you want to bias the NPN output transistor on, which in most hi fi op amps (Not rail to rail output) this is the one connected to the top rail.

I haven't looked up this CRD, but Its likely fine for most. Tweaking the current would be a nice feature, and likely have some benfit.

Anyone know who makes the CRD discussed so I can look it up?

Also, just a genral comment, and maybe Jan-peter could pipe in, is there any reason at all to force this seperate supply to the amp board. That is to say, can't you just do the whole op amp diff amp input and the supply, like several if need be, on a different board. Wouldn't that be more ideal?

Regards,

Mike
Click to expand...


Just search for SST511, I got mine from Mouser and I think I got the datasheet also via the Mouser internet site.

Gertjan
 
#128
maxlorenz said:
I have a question regarding bias mod, 'cause I'm tempted to try it.

J511 is only good for AD8620, wright?
In that case, can someone point me to suitable CDR and/or Jfet to mod the 5532 and BurrBrown 2134 opamps?

It is not that I'm lazy but honestly I don't feel capable of calculating bias current :angel:

Gratefully yours...
Mauricio
Click to expand...


Portlandmike said:



Mauricio,

current source to the negative rail will work with most any op amp, and best I suspect too. 5532 and I think the 2134 too.
The reason is NPN's are usually better than PNP's, so you want to bias the NPN output transistor on, which in most hi fi op amps (Not rail to rail output) this is the one connected to the top rail.

I haven't looked up this CRD, but Its likely fine for most. Tweaking the current would be a nice feature, and likely have some benfit.

Anyone know who makes the CRD discussed so I can look it up?

Also, just a genral comment, and maybe Jan-peter could pipe in, is there any reason at all to force this seperate supply to the amp board. That is to say, can't you just do the whole op amp diff amp input and the supply, like several if need be, on a different board. Wouldn't that be more ideal?

Regards,

Mike
Click to expand...


BB opa2134 actually needs to be biased to the positive rail, I haven't checked for the 5532. More than biasing the output into class mostly A, also has to do with fixing the psrr difference in rails brought on by miller compensation. You'll find more info on that in old posts.
 
#130
t. said:
Well hopefully I'll try these regs I knocked up to power the AD8620's sometime during the week if I get time
Just trying to see the best way where to fit the +/- wires to try and keep it neat, the track is so thin
Click to expand...

I was wondering did you ever tried these nice two boards?
And the two 470u are you using are that Panasonic FC's?

Bastiaan
 
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