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1bit DAC in sigma-delta DAC

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Yun Lin

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I just wonder why 1bit DAC should be designed by switch capacitor circuit.
If I design it by only inverter .what is the problem. The inverter is more simple.
Thanks in advance!
 

gigle

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A simple inverter may be a good choice for the 1-bit DAC followed by continuous time filter. The possible problems of this DAC are 1) clock jitter and 2) rise and fall time mismatch of the 1-bit DAC (inverter).
 

Yun Lin

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gigle said:
A simple inverter may be a good choice for the 1-bit DAC followed by continuous time filter. The possible problems of this DAC are 1) clock jitter and 2) rise and fall time mismatch of the 1-bit DAC (inverter).
Thanks firstly:D. For the first problem you list, I think the clock jitter still effect the switch capacitor, right? Because the switch capacitor circuit still be controled by clock.
I agree with you by problem 2.
Thanks again.
 

gigle

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Yes, you are right.

But as long as the BW of the OTA is large enough, a SC filter is less sensitive to clock jitter than a CT filter. The requirement of high BW OTA is the drawback of the SC filter.

Thanks
 

hysamir

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hey guys off from yr question, i need to design 8 bit a/d converter in cmos, for that i need to design 1 bit d/a. give me some guideline to start my work..

for a/d basic blocks are integrator, comparator and d/a. can u give me some links or guideline which deals with mainly on design cause i know theory behind this.

thakx, yr reply is appreciated.
 

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