how to extend a 8bits DAC pecision to 10 bits 12bit and more

Hello, 

Not sure if I fully understand the question, but if you need a 10-bit DAC why did you buy an 8-bit DAC?... I do not mean to be cavalier about it, but if DAC resolution could be easily increased through software, why would ADI offer HS DACs with 8, 10, 12, 14, and 16-bit variants, each priced according to their resolution?

A good 14-bit alternative to the AD9708 is the AD9744. AD9740 and AD9742 are its 10-bit and 12-bit variants, with AD9740 is priced similarly to AD9708. 

AD9744 Datasheet and Product Info | Analog Devices 

Landsman

Hello, 

Not sure if I fully understand the question, but if you need a 10-bit DAC why did you buy an 8-bit DAC?... I do not mean to be cavalier about it, but if DAC resolution could be easily increased through software, why would ADI offer HS DACs with 8, 10, 12, 14, and 16-bit variants, each priced according to their resolution?

A good 14-bit alternative to the AD9708 is the AD9744. AD9740 and AD9742 are its 10-bit and 12-bit variants, with AD9740 is priced similarly to AD9708. 

AD9744 Datasheet and Product Info | Analog Devices 

Landsman

thank you so much .what I think is  I already put   a AD9708 in  my system( E-board)，it used to work  good for my system, however , I want to decrease the system noise to work better ,but I don't want to make a new board.  so  I want to know is there any way to improve DAC resolution in software. according to my knowledge , some way called sigma-delta modulation  may help , but I don't  how .

I also want  to  buy a single bit DAC, Do you have any recommendation ?

Hi Hhhcwx,

Sigma-delta is a specific converter architecture which sacrifices BW for improved noise spectral density across a narrow band. I am not sure on the processing requirements for such as setup. One would basically use noise-shaping to post process the data, assuming the carrier is at a low enough frequency. I am not sure on the best way to AD9708 implement this on an FPGA with a current-steering or a voltage DAC. But it can be theoretically done.   

update: you may find the following application note interesting:

Sigma-Delta ADCs and DACs Application Note (AN-283) (analog.com)

Landsman 

ADI offers delta-sigma DACs and ADCs, please check the selection table on analog.com.  

is  there any single bit DAC in ADI ? I want to buy one   

I read some arcticles ，I  don't  complete the sigma-delta DAC actually , only on theoretically (simulation in Simulink) I design a modulator and work well .I  want to get some actual recommendations  .