How to improve current mirror error (Iin & Iout) ?

[jiachang]

current mirror error

i used cascode current mirror to generate around 238nA constant current for cap. charging.
But i always got Iout= 233nA to 242nA varation during charging period.
How can i keep the Iout constant?

Thanks

 

[venkateshr]

what is current mirrors-errors

Hi jiachang ,
It is very good to use to have cascode mirror for this precise replication .even though it is a feeble difference due to diff in VDS between actual and mirrored (or finite op impedance ) it may be noteworthy in some cases. I think cascode with more stacks(>2) can multiply the op. resistance thereby bringing down the difference

p.s :If supply voltage is a constraint .WIDE SWING CASCODE will help u .

Added after 4 minutes:

Jiachang ,
You can use longer L(also W by same factor) but maintaining the same W/L ratio so that op resistance is increased .

 

[holddreams]

current mirrors-errors

you can refer this paper -----"DESIGN AND OPTIMIZATION OF A HIGH PSRR CMOS BANDGAP VOLTAGE REFERENCE".

Try.

 

[tbksandeep]

what is a current mirror-error

jichang u can vary w/l ratio first and see it.one important suggestion is use active loads.since ur loking for a current of such a low value i would suggest active loads..did u use diff amplifier at the input?if u have not done so do it and try it.u might get better results.