IV for PCM1730

MWP · 14th October 2002, 03:28 PM

Hi all...

The PCM1730 has balanced current outputs labeled as IOUT+ and IOUT-.

The PDF shows a "typical" IV stage which consists of a opamp based IV for each half of the output followed by a summing opamp.

I wish to stick to opamps for the IV (OPA637's), but was wondering if i can use only one half of the output which will cut the number of opamps needed.

I found a web site which shows the same DAC with this output stage:

Will i be comprimsing the quality of the DAC by only using 1/2 of the output like the diagram above?

ftorres · 17th October 2002, 07:16 AM

Not quite related, but have a look at this thread I tried to start

. Haven't had the time to test it, but I'm still considering using this chip.

peranders · 17th October 2002, 09:32 AM

Quote:

Originally posted by MWP
I wish to stick to opamps for the IV (OPA637's), but was wondering if i can use only one half of the output which will cut the number of opamps needed.

OPA637 is not intended for low gains. Use OPA627 instead if you have gain < 5.

MWP · 17th October 2002, 12:55 PM

I think im just going to go with the original circuit.
Will be a pain to route on the PCB as it will be using 8 separate 8pin opamps... but its all part of the fun

Petter · 17th October 2002, 01:52 PM

Half the output:

Yes as you have drawn it, quality will suffer. However, if you require only single ended outputs use Iout+ and Iout- on a fully balanced op-amp such as THS4131. You probably don't even need the output buffer, and you certainly don't need R6,7 ...

Petter

14th October 2002, 03:28 PM	#1
MWP diyAudio Member Join Date: Oct 2002 Location: Adelaide, South Australia	IV for PCM1730 Hi all... The PCM1730 has balanced current outputs labeled as IOUT+ and IOUT-. The PDF shows a "typical" IV stage which consists of a opamp based IV for each half of the output followed by a summing opamp. I wish to stick to opamps for the IV (OPA637's), but was wondering if i can use only one half of the output which will cut the number of opamps needed. I found a web site which shows the same DAC with this output stage: Will i be comprimsing the quality of the DAC by only using 1/2 of the output like the diagram above?

17th October 2002, 07:16 AM	#2
ftorres diyAudio Member Join Date: Apr 2001 Location: Limoges, France	Not quite related, but have a look at this thread I tried to start . Haven't had the time to test it, but I'm still considering using this chip. __________________ François "Learning French is trivial: the word for horse is cheval, and everything else follows in the same way."

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17th October 2002, 12:55 PM	#4
MWP diyAudio Member Join Date: Oct 2002 Location: Adelaide, South Australia	I think im just going to go with the original circuit. Will be a pain to route on the PCB as it will be using 8 separate 8pin opamps... but its all part of the fun

17th October 2002, 01:52 PM	#5
Petter diyAudio Member Join Date: Jan 2001 Location: Scandinavia	Half the output: Yes as you have drawn it, quality will suffer. However, if you require only single ended outputs use Iout+ and Iout- on a fully balanced op-amp such as THS4131. You probably don't even need the output buffer, and you certainly don't need R6,7 ... Petter

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