setting output reference level of DAC.

[malstew]

I am using a DAC to generate a composite video output signal (1Vpp). The problem is that I output between 0V and 1V at the DAC output and need -0.286 to 0.714V at the TV input.

Can anyone tell me how this is done? Do I use a resistive divider to "Ground" level of the COAX cable to 0.286 volts at the source?

Thanks for any help.

 

[Vamsi Mocherla]

Actually you can design a current source which will give enough current to create the SYNC level over the load resistor. The DAC part will take care of the signal from 0.286 to whatever.

 

[malstew]

I think I got my answer.. so I will post it here.

The source and destination are AC coupled so it doesn't matter that the signal doesn't go negative out of the DAC. It only matters that the output is at the right levels.

Does this make sense?

 

[oldtree]

pls continue

 

[Vamsi Mocherla]

Yes, you are true...Anyways, the design is such that you do not drive any negative levels. That is the reason why you have a SYNC level.