Timeline for Best way to attenuate R2R DAC output?
Current License: CC BY-SA 4.0
14 events
| when toggle format | what | by | license | comment | |
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| Oct 31, 2019 at 16:02 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jun 27, 2019 at 20:02 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Feb 23, 2019 at 20:00 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
| Jun 20, 2018 at 1:25 | comment | added | C. Towne Springer | Emitter follower. | |
| Jun 19, 2018 at 21:42 | answer | added | Spehro 'speff' Pefhany | timeline score: 1 | |
| Jun 19, 2018 at 19:43 | comment | added | glen_geek | Seems to me that a raw R2R ladder outputs a current. If you desire an output voltage, you might consider a current-to-voltage converter stage having very low input-impedance. An inverting high-speed op-amp and a feedback resistor comes to mind. | |
| Jun 19, 2018 at 17:55 | comment | added | Chris Stratton | It's a thought process to getting to an end result using the concepts you are already employing - the end result itself would be simpler. Sometimes a spreadsheet program is good for playing with ideas like this. Or write a little custom code to chart the possibilities. Or use a circuit simulator, but those don't tend to be ideal for exploring a multidimensional set of possible changes. | |
| Jun 19, 2018 at 17:53 | comment | added | Connor Spangler | @ChrisStratton interesting solution! Seems a bit... cudgeled though? | |
| Jun 19, 2018 at 17:51 | comment | added | Chris Stratton | @Answoquest - Conceptually one way you could do it would be to design your DAC with some additional high order bits that you only ever drive as zero - ie, go from 8 to 10 bits and now your maximum is 1/4 of the previous voltage. Then you could simplify the redundant components into a smaller number. I believe if you study the result you'll be able to see how you could then use different values to create a gain fraction which is not a power of two, but I haven't actually done it on the back of an envelope. | |
| Jun 19, 2018 at 17:48 | comment | added | Connor Spangler | @ChrisStratton even if designing for the load impedance, how would you factor in the specific output voltage? I understand how to design an R2R DAC with a max output equivalent to the input level, but not with a specific lower gain. | |
| Jun 19, 2018 at 17:45 | comment | added | Connor Spangler | @jonRB current draw would never exceed 40 mA, and load impedence would be 75 ohms. For the purpose of making this question/answer more useful for everyone, I would be interested in the answer for high vs low current draws and high vs low load impedances. | |
| Jun 19, 2018 at 17:44 | comment | added | Chris Stratton | VGA would be 75 ohms, unless someone forgot to terminate it. Essentially, one either designs the ladder for the load impedance, or you need a suitable amplifier (video amplifier is a category) with less than unity gain or with an output divider including the load impedance. Also, given likely AGC it may not matter, as long as electrical maximums are not exceeded. | |
| Jun 19, 2018 at 17:41 | comment | added | user16222 | depends... how much drive strength do you need? what is the load impedance? | |
| Jun 19, 2018 at 17:22 | history | asked | Connor Spangler | CC BY-SA 4.0 |