How we can implement one resistor in standard cmos process?

[me_forouzan]

Accurate resistor

Hi

How we can implement one resistor in standard cmos process with good accuracy?
I design one circuit that is sensitive about resistor variation. I know implementing resistors in CMOS process have about 25% tolerance. please help me.

 

[littlej_zju]

Accurate resistor

Firstly, you can use large size resistor. Such as, w>1um, l>1um, and l/w>2. Large size can avoid poly and SAB variation.
Secondly, you can use parallel resistors.

 

[Fom]

Accurate resistor

You need good accuracy or matching property?

 

[me_forouzan]

Re: Accurate resistor

I could optimize my circuit with some special resistor value. But i am worry that if i fubricate this IC ,maybe the value of resistor change and the circuit performance degrade. I want to know can i implement these resistors with some special method that implement resistors accurately.

 

[JoannesPaulus]

Accurate resistor

If it is an absolute resistor value that you need to achieve, you will need to use some sort of calibration. If you need a ratio of two resistors, you can get that to almost any accuracy, like 0.1%.

 

[wpchan05]

Re: Accurate resistor

why not use external resistors?

 

[me_forouzan]

Re: Accurate resistor

I heared about thin film resistor that can implement very accurate resistor.
Are these kind of resistors implementble in CMOS technology? these kind of resistor need more area or not?

 

[Fom]

Re: Accurate resistor

I think they use laser trimming.

 

[edge_tv]

Accurate resistor

Don't use resistors, if accuracy is needed. For example if you trie to move the zero in a miller compensation with a resistor you will run into problems. Accuracy is not the only problem, temp variations are also a bad habbit of such things.