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What kind of resistor do we use for LDO?

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pugongying

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In LDO,we require large resistors about 100k~200K ohm,can we use n-well resistor? How about the matching ?Thanks!
 

panyi

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Normally,we use P+ poly resistor without silicide.

About match issue, you can read the book "The Art of Analog Layout".
 

qutang

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I think poly res is suitable
 

jttzeng

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My understanding, Poly_RPO resistor process varition is bigger ther NW resistor. But, NW resistor will take more area larger than poly resistor for min. rule. BTW, the temperature coefficient of ploy resistor might be opposite to NW resistor.
 

leo_o2

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N-well resistors is voltage-dependent
 

stoned

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hi jttzeng

I don't think so, the value of NW resistor can reach about 2k, but p+ resitor wothout silicide is about .32k, so the area is smaller
 

surianova

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pugongying said:
In LDO,we require large resistors about 100k~200K ohm,can we use n-well resistor? How about the matching ?Thanks!
the resistor look quite large, will contribute high termal noise at high temperature.
 

leo_o2

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Hi stoned,

You must take into account: min width of Nwell res is much bigger than min width of P+Poly res. And the min space of Nwell res is also much bigger than min space of P+Poly res in design rule.
For final conclusion, all of these must be considered.
 

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