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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Low Noise 8 Bit DAC https://designers-guide.org/forum/YaBB.pl?num=1324532547 Message started by analog_design on Dec 21st, 2011, 9:42pm |
Title: Low Noise 8 Bit DAC Post by analog_design on Dec 21st, 2011, 9:42pm Hi Guys, I need to design Very low noise 8 bit DAC which should have integrated noise less than 50 uV. It is voltage DAC with 1 MHz BW. I do not want to use Current steering topology which will again need I/V Amp which would add more noise. Please, suggest me architecture. Thank You & Take Care |
Title: Re: Low Noise 8 Bit DAC Post by raja.cedt on Dec 21st, 2011, 11:17pm hello, are you sure? because the moment you say 8 bit integrated noise will be fixed. Thanks, raj. |
Title: Re: Low Noise 8 Bit DAC Post by raja.cedt on Dec 22nd, 2011, 1:52am in fact capacitor charger based dac is voltage dac, but finally you need an opamp i guess otherwise you need to find some thing to buffer it out. |
Title: Re: Low Noise 8 Bit DAC Post by loose-electron on Dec 22nd, 2011, 4:03am your quantization noise at 8 bit and 1 V full scale amplitude is bigger than your noise specifiied. Does not make sense. |
Title: Re: Low Noise 8 Bit DAC Post by RobG on Dec 22nd, 2011, 11:12am loose-electron wrote on Dec 22nd, 2011, 4:03am:
I'm guessing it is a reference bias with trim to manage for process and DES* corners. Integrated noise is going to be limited by how much filtering you can have, so I think the best approach would be the simplest: an 8 bit tapped resistor dividing down a reference voltage and feeding an RC low pass filter. *Design Engineer Skill |
Title: Re: Low Noise 8 Bit DAC Post by Lex on Dec 23rd, 2011, 12:17am loose-electron wrote on Dec 22nd, 2011, 4:03am:
Sure it makes sense. If it is a DC setting, you won't have quantization noise. ;) I would suggest placing a large capacitance at the output. |
Title: Re: Low Noise 8 Bit DAC Post by raja.cedt on Dec 24th, 2011, 4:01pm hello lex, what do you mean by dc setting? thanks, raj. |
Title: Re: Low Noise 8 Bit DAC Post by loose-electron on Dec 25th, 2011, 4:07pm "it is a voltage DAC with 1MHz BW" That does not sound like an set and forget DAC... |
Title: Re: Low Noise 8 Bit DAC Post by ywguo on Dec 25th, 2011, 5:30pm I like RobG's solution. Easy to implement. -- Yawei |
Title: Re: Low Noise 8 Bit DAC Post by RobG on Dec 25th, 2011, 8:48pm loose-electron wrote on Dec 25th, 2011, 4:07pm:
Yeah I missed that, but I think the solution is the same. Integrated noise power is kT/C = (50uV)^2, so the only thing left to determine is the R for the filter. I get 1.6pF for the cap and 96k for the resistor at room temp, but would use as large a cap as I could afford and lower the resistance accordingly. rg |
Title: Re: Low Noise 8 Bit DAC Post by loose-electron on Dec 26th, 2011, 12:53pm No follow up from the OP, so no clarification on what they wanted. |
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