Timeline for How does exactly this DAC work?
Current License: CC BY-SA 4.0
15 events
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| Apr 5, 2022 at 20:59 | history | edited | pat | CC BY-SA 4.0 |
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| Apr 5, 2022 at 20:59 | comment | added | pat | Added simulation example in ltspice. | |
| Apr 5, 2022 at 19:38 | vote | accept | Scipio | ||
| Apr 5, 2022 at 19:08 | comment | added | pat | In this case we assume they are the same (thermometer coded). They could also be weighted as binary or another scheme. I highly suggest to build this in a simulator like ltspice. Use a very simple current mirror (two transistors) to understand the mechanisms. | |
| Apr 5, 2022 at 14:57 | comment | added | Scipio | @pat So the currents I1=I2=... could also be called unit current sources because they are all the same? But if they are all the same the output voltage for codes d1,d0 = 1,0 and d1,d0 = 0,1 would be the same? Also, assuming that this DAC has a reference voltage of 1V what would be the value of the Ilsb current (which i presume here is I1=I2=...)? | |
| Apr 5, 2022 at 0:15 | comment | added | pat | @GotBlackOps. Q3 and Q4 have same S and G voltages, so same current. That is basic mirror (assuming load mirror does not vary too much). If a control switch is off all the current will flow to the load node via the fixed switch. If a switch is on, half will flow to load and half through the switch. | |
| Apr 4, 2022 at 23:58 | comment | added | SteveSh | If the gate voltage on Q3 is the same as it is on Q4, then the current sourced by Q3 will be identical to that sourced by Q4. This applies to all the FETs to the right of Q4. And this relationship holds so long as the characteristics of all the FETs are identical. If that's not the case, then the currents will be different, even with the same gate voltage. | |
| Apr 4, 2022 at 23:51 | comment | added | Scipio | Also how does the current from Q3 is the same as the corrent from Q4? They only share the same gate but their source voltage is different and so is VGS and with that the current value | |
| Apr 4, 2022 at 23:41 | comment | added | Scipio | What values does I1 and I0 have? What is their expression? I dont think they can be equal, atleast have a difference of 2x from each other. So If d1 = 1, I1 =1/2 so if every bit is 0 i would get maximum output voltage (when i should get 0V)? How does all this translates to the DAC transfer function Dout(Din) = code * Vlsb? | |
| Apr 4, 2022 at 23:12 | history | edited | pat | CC BY-SA 4.0 |
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| Apr 4, 2022 at 23:10 | comment | added | pat | link added to post. | |
| Apr 4, 2022 at 23:07 | history | edited | pat | CC BY-SA 4.0 |
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| Apr 4, 2022 at 23:06 | comment | added | Scipio | Do you have any good sources in this basic fully differential current steering dac? Cus i dont find anything usefull. | |
| Apr 4, 2022 at 23:04 | history | edited | pat | CC BY-SA 4.0 |
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| Apr 4, 2022 at 22:59 | history | answered | pat | CC BY-SA 4.0 |