DAC

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Gopal Adhikari

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I have been learning electronics and ltspice for some time now. I am stuck here. any help appreciated.
I have to simulate a gray code input R-2R DAC as given in the link below
https://www.google.co.jp/search?q=gray+code+R-2R+ladder+dac&rlz=1C1LENN_enJP649JP649&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiU54aIoOnKAhUBX5QKHaPZABIQ_AUIBygB&biw=1366&bih=677#imgrc=aSOuYx3wZVy-7M:

I am stuck in figuring out the switch used in this circuit. i want to simulate this circuit using simple switches. Can anybody suggest how to simulate this circuit. I am reallly in trouble figuring out the switches.
Help with drafts, simulation figures etc will help me.

Thanks in advance.
Gopal
 
Hi

I've attached a zip file containing a demo using LTspice.
I couldn't see the type of switches used in the diagrams you linked to.
 

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  • R-2RDAC.png
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  • R-2RLadder.zip
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eTech said:
Hi

I've attached a zip file containing a demo using LTspice.
Click to expand...



Thanks eTech,

Thank you so much. I have already done for simple R-2R Voltage mode and Curret Mode DAC. I cannot figure out to switch for the figure. I think the switch would operate as shown in the figure attached.
 

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  • switch.jpg
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I have not tried this but I think it will work. Note I reversed the inputs of the middle two switches. You might to remove the "ground" and make it a voltage that is 1/2 of what a "1" is. So it will see a "0" as "-" and "1" is "+".
 
Gopal Adhikari said:
Thanks eTech,

Thank you so much. I have already done for simple R-2R Voltage mode and Curret Mode DAC. I cannot figure out to switch for the figure. I think the switch would operate as shown in the figure attached.
Click to expand...

Here is switch model based on your diagram.
 

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  • SWFUNC1.zip
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eTech said:
Here is switch model based on your diagram.
Click to expand...
Thank You eTech. your switch model works as needed. Further more, I need to know the internal circuitry for the switch. I am afraid but Can you please send me the internal diagram for switch. I think you designed the switch using the SW from LTSPICE. Or did you do something else. I am poor at reading netlist.
Thanks in advance.
Gopal
 
Last edited:

Hi

I've uploaded the block version of the model.

And yes, I used the SW device, and a BUF device from LTspice.
Have fun.
 

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  • SWFUNC1Blk.zip
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