Limiting referred noise in bandgap circuit

[ccw27]

noise in bandgap

Is the output referred noise of the current reference solely dependent on ADC requirement?

Do we can about output referred noise of PTAT current. If yes, how can I improve my PTAT output referred noise. I am using a conventional cascode Bandgap circuit under 3V supply voltage.

Thanks

 

[jiangwp]

Re: noise in bandgap

Do you use the PTAT to bias the op amplifier of BandGap?

If so , i think you can add the decouping capacitor to filter some high frequency noise to get a relative constant current mirror. so this reduces the noise of op amplifier to decrease the effect with the noise.

 

[paladinzlp]

Re: noise in bandgap

I think that capacitor is added between current mirror PMOS 's gate and gnd.
Cadd>>the capacitor between PMOS's gate and output

 

[blue_orangee]

noise in bandgap

To paladinzlp
Why not between PMOS's gate and vdd.

 

[andy2000a]

noise in bandgap

add Pmos gate to Vdd cause PSRR slow , someone
use nmos cap on Vbg connector to Gnd path .

but add pmos gate also reduce PSRR ..

 

[paladinzlp]

noise in bandgap

If your vss=gnd , between PMOS's gate and vdd, the
PSRR+ low when high frequency!
If your vss=-3v ,between PMOS's gate and gnd ,the
PSRR- low when high frequency,between PMOS's gate and vdd , PSRR+ low when high frequency!

Added after 34 minutes:

Sorry! renew the information.
If you vss=-3v ,between PMOS's gate and gnd ,the
PSRR+ and PSRR- all OK!

 

[ccw27]

Re: noise in bandgap

For bandgap at what frequency should we be looking at for output referred current noise? 100kHz? Also how can I decrease thermal and flicker noise?

Thanks