Implementation High R in CMOS

[rampat]

How to implement high resistance of MegaOhm orders in CMOS .Actually this is needed for my filter design..And which are the process available that has high res and high cap density ?

 

[amarendrap14]

use N-well resistors for high values,although area will still be high for Mohms..
generally MOS capacitors are used to implement cap of the order of pF.. u can try DRAM capacitor technology for high density....

 

[ambreesh]

Gate poly which is not metalised gives high resistance in range of 1K/sq.
Has good VC and TC. Also the minimum width for 0.18 process could be as small as 1.5u

 

[sunjimmy]

The ony way to achieve high R with reasonable area is MOS device. You may need to design some kind of calibration/ or tracking ckt to control its value.

 

[iamxo]

Mos device can be used as pseudo-resistors.
And it has large value of Meg ohm.

 

[lijianheng]

N well resistor has the largest resistance.

For MOhms resisitance you can use mos resistor by adding bias and calibration circuit.

 

[rampat]

Do you have any papers for this type of hieg res implementaion using MOS with calibaration

 

[gevy]

You can use switched capacitor filter.

 

[rampat]

But i will be having high frequency sswitching noise at the o/p...
i don want this noise to be couple to my analog output

 

[ambreesh]

how many Mohms do you have to implement?

 

[rampat]

2MOhms which is requiresd for low frequency opamp application...

 

[ambreesh]

If you have high rho poly resistor with 1K/sq resistance, and minimum width of 1.5u you would be requiring 3000sq micron of silicon area.
Well I would say cheap and has better performance compared to MOS resiator or Nwell resistor

 

[rampat]

Thanks anbreesh..So i can go for 0.18u process nw.

 

[Sadegh.j]

I think you use an IC resistor

 

[buckaroo]

SC is not a resistor indeed! because it can not provide DC bias

You can use switched capacitor filter.

Added after 1 minutes:

The ony way to achieve high R with reasonable area is MOS device. You may need to design some kind of calibration/ or tracking ckt to control its value.

would u plz explain it deeply, or recommond me some paper, thanks a lot

 

[solidstate]

check this out:

J. A. Geen, S. J. Sherman, J. F. Chang et al., “Single Chip Surface Micromachined Integrated Gyroscope With 50°/h Allan Deviation,” IEEE J. Solid-State Circuits, Dec. 2002.