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I would like to use COD with Legato 3.1 I searched your forum topics and found that it was recommended to use 357R for I/V resistors and 1.5K for CCS resistors. For Legato 3.1, I/V resistors are R1/2/3/4 and CCS resistors are R9/10/11/12. However, it says in the manual : Quote:If you want to change the output voltage you need to adjust both the top - I/V (R1-R4) values and bottom -
CCS (R9-R16) values in proportion to each other. I have found that a ratio of 1/4.4 works very well for top
resistor values up to about 364Ω. I have not tried gain any higher than that. If you need to please contact
us. I would like to use 270R for I/V resistors and 1.2K for CCS resistors. Will this be ok with COD dac? One more question, do I have to change any other resistors in Legato 3.1 circuit including SE stage besides these? (Anything around the opamp?)
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Rank: Administration
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I would personally try the higher values first, but the values you mentioned should work too.
You don't need nay further changes. :)
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Rank: Member
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Joined: 7/6/2012(UTC) Posts: 3 Location: Rio de Janeiro
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Originally Posted by: Russ White  I would personally try the higher values first, but the values you mentioned should work too.
You don't need nay further changes. :) First off, thank you for the reply. My understanding is the higher those get, the less current Legato will flow, correct? If less current will flow through I/V and CCS resistors, can I use 1/2W instead of 1/4W resistors if I use 357R for I/V and 1.58K for CCS?
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Rank: Member
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Joined: 7/6/2012(UTC) Posts: 3 Location: Rio de Janeiro
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I ran a spice simulation and seems like 1/4W resistors will be alright if I use 357 & 1.58K resistors.
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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Yes, they should be just fine. 1/2W might be better for the CCS, but even they should be ok.
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