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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> The VDD variation of DAC. https://designers-guide.org/forum/YaBB.pl?num=1102315277 Message started by Question on Dec 5th, 2004, 10:41pm |
Title: The VDD variation of DAC. Post by Question on Dec 5th, 2004, 10:41pm I design a DAC, using current steering architecture. The base current source cell likes the picture below. ![]() The bias voltage come from bandgap circuit. it is steady. But the VDD will have 5% to 10% fluctuation becaues of the source out of the chip. So the output current will change a lot by different VDD voltage. How can I slove this problem? Please give me some advice. It is emergency!! Thank you very much. |
Title: Re: The VDD variation of DAC. Post by 101questions on Dec 6th, 2004, 1:16pm The bandgap output voltage should be referred to VDD. Then VDD ripple infuence would be somewhat reduced. |
Title: Re: The VDD variation of DAC. Post by sheldon on Dec 10th, 2004, 5:58pm Greetings, You did not say much about the design of the bandgap. Another approach when the bandgap is ground referenced is to use : 1) a V-I converter to convert the bandgap voltage reference voltage to a stable current, effectively an n-channel current source. 2) Convert the single transistor current source into a p-channel current mirror. A single diode connected transistor can bias all the DAC current sources. This will eliminate the sensistivity of the current source to power supply voltage variations. |
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