Hi, i need to know if this DAC-op-amp calculation is ok

AI Thread Summary
The discussion revolves around the calculation of output voltage in a DAC using an R2R ladder configuration. Participants express confusion over the initial voltage calculation, which incorrectly suggests an output of 10V from a +/-9V power supply. There are discrepancies noted between resistor values in the schematic and those in a provided table, leading to further clarification requests. The conversation highlights the importance of understanding the differences between binary weighted networks and ladder networks in DAC design. Overall, the participants seek to resolve these calculation and schematic inconsistencies for accurate DAC implementation.
NYAME EPHRAIM
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ephraim summing amp.PNG

Homework Statement

Homework Equations

The Attempt at a Solution

 

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That doesn't look right to me. You also can't get 10V out if the power supplies are +/-9V.

Are you trying to make an R2R ladder DAC?
 
berkeman said:
That doesn't look right to me. You also can't get 10V out if the power supplies are +/-9V.

Are you trying to make an R2R ladder DAC?
Hi, thanks for the reply, the diagraim was presented that way for me to do the calculations, i have also seen related diagraim online for DAC!
Yeah it,s ladder
 
Well, can you explain this first line from your diagram? It doesn't make sense past the 900mV number...

Vout = (9V x 470/4700) = 900mV = 800mV = 8V

And why are the resistor values in your table different from the schematic?
 
berkeman said:
Well, can you explain this first line from your diagram? It doesn't make sense past the 900mV number...

Vout = (9V x 470/4700) = 900mV = 800mV = 8V

And why are the resistor values in your table different from the schematic?

Hi thanks for the reply. my target is to fill that table, those value of resistor in that ladder circuit we don't have most of the values practically, that's why i had to reduce the 9 to 8.
please take a look at this diagram and cross check.
FINAL CHECK EPHRAIM.PNG
 

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That looks very close. The only problem I see is maybe the units definition for Vout in the last column heading of the table. It is hard to read the image, it shows 'x (something) 100mV'. What does it actually say?

What you have shown is a Binary Weighted network.

A Ladder network is shown below. (From: https://en.wikipedia.org/wiki/Resistor_ladder)
336px-UnequalLadder.svg.png

To learn more, try a Google search for both terms.

Cheers,
Tom
 

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