A Small Network Analysis Problem - Urgent - Please help...

[purifier]

The following image shows a R-2R Ladder DAC for Switch Positions 001. The solution too is given below... but i'm unable to get a hold of how the solution was arrived. Maybe i'm missing something but i used the Virtual Ground Concept and Voltage Division Rules but i'm still not getting it. Can someone help me get to the solution? I want to know a detailed procedure as to how those Nodal Voltages were obtained... Please help...

I guess there's no more need for this image... I've got a solution. Thank you very much everyone...

 

[uk]

Re: A Small Network Analysis Problem - Urgent - Please help.

write down the circuit equations for feedback circuit: remember that the gain of an opamp is infinite in ideal. Use infinite gain in these circuit equations. At the and u will grab the gain values for the points

 

[purifier]

Sorry but didn't get you.. It is only that i'm writing some incorrect equations. The negative terminal is at the Virtual Ground. So R||2R= (2R/3) which is in series with R= (5R/3) which is parallel to 2R and so on... I used this to some extent but later resorted to some other ways but didn't get it... You mind being a little more detailed?

 

[purifier]

Someone please help... I have an exam tomorrow...

 

[Kral]

Re: A Small Network Analysis Problem - Urgent - Please help.

purifier,
The easiest way to solve this type problem is to assume the NI input of the OP Amp is at virtual ground.
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Assume the voltage at the junction of the rightmost R-2R-R junction is 1 volt.
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Calculate the current through the left-most R, based on the 1 volt assumption.
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Calculate the voltage at the "input side of this R, based on the current calculation above.
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Continue this process untill you reach the input. Call the calculated input Vr'
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Scale the node voltages by a factor equal to Vr'/Vr.
Regards,
Jon

 

[purifier]

Thanks a lot... That helped... Though the exam is over... It'll help me for sure... Thank You once again..