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[SOLVED] about cmos bandgap accuracy

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andy2000akimo

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If I use tradation OPA + 2 diode cmos bandgap ..

how about this type accuracy ?

target is accuracy  < 1mv  VCC=5v
and temp from -50 ~ +155 .

but , I think if I need < 1mv , at first , I need offset small than 1mv OP AMp .
which architecture OPA can meet this specification ? or use Auto zero OP Amp ?
 

prcken

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i think it's really hard to design precision CMOS bandgap due to mismatch and offset of MOSFETs are more serious than BJTs.
there are some published papers focusing in this, but dont know whether it can be really used in chips for production.
 

andy2000akimo

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Hi ..
in cmos design usually use parastic pnp.but some hi volt proces have
"VNPN" maybe vnpn will more accuracy than PNP device ..

some current mirror circuit need high accuracy current ,
and I think use bandgap provide 1% accuracy => 0.5mv
use 600mv bandgap design -> devide to 50mv

and I want use low offset OPA + external resistor , maybe can get high precision current .

but low offset OPA I only know auto zero (someone call Chop or CDS ?)
. auto zero (use PIP cap) can meet 0.5mv offset ?
 

snafflekid

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andy2000akimo,

I think that you will need to use an auto-zero amplifier. There are also switched capacitor bandgap designs that would work
 

hackjiang

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Frankly speaking. a 10 mv variation can be expected in Vbe across corner. To get such a accuracy of <1mv, you have to add trim circuitry.
 

tpeng

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it is hard for accurency always 1mV with temp from -55 to 155 degree by trim method.
 

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