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Design >> Analog Design >> nA current reference
https://designers-guide.org/forum/YaBB.pl?num=1227607468

Message started by manodipan on Nov 25^th, 2008, 2:04am

Title: nA current reference
Post by manodipan on Nov 25^th, 2008, 2:04am

Hi guys,
can u guys suggest some very good current reference of around 10 nA with very little sensitivity to process,temperature etc...thanks

Title: Re: nA current reference
Post by raja.cedt on Nov 25^th, 2008, 2:42am

hi manodeepan,
i have some questions regarding u r questions.1.For what application u need this 2.in which technology.why i am asking is i am working in 65nm, in this technology even 5*1 mos transistor have around 6nA gate current.so may be u can get 10nA reference in older technologies,but here it is very difficult(for getting presise reference u need to use -ve feed back,so inherently u have to mos). so ples etell me the which tech nod eu r working so that we can think about circuit.
Thank you

Title: Re: nA current reference
Post by thechopper on Nov 25^th, 2008, 6:38pm

Check this reference

"CMOS Current Reference Without Resistance"
Henri J. Oguey and Daniel Aebischer

IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 32, NO. 7, JULY 1997

Regards
Tosei

Title: Re: nA current reference
Post by manodipan on Nov 27^th, 2008, 1:14am

Hi Raja,
The technology is 130 nm and current linearity is also an important factor...

Title: Re: nA current reference
Post by raja.cedt on Nov 27^th, 2008, 2:22am

hi manodeepan,
what do u mean by linearity.i guess its a current reference.do you want controlled current reference?
Thank you.

Title: Re: nA current reference
Post by manodipan on Dec 2^nd, 2008, 2:14am

Hi raja,
You are right it's a current reference with very less process and temperature sensitivity and good o/p resistance throughout the o/p range..

Title: Re: nA current reference
Post by rf-design on Dec 15^th, 2008, 1:51pm

Regarding gate leakage you can use possible thick-oxide devices used for output driver stages. The gate and the channel leakage is much lower.

For the nA-current source I suggest to start with a higher current level. So for instance using a bandgap and driving a low tempco resistor with current to equal the bandgap voltage.

Then use a current divider which is made of a mirror MOS pair where the low current source is shifted by a voltage equal to

log(a)*m*Vt

m: subthreshold factor, Vt: temperatur voltage, a: current division factor

This exponential current multiplier voltage should be derived from the k*T-Cell made of MOS instead of parasitic PNP's

The you can get very low current in some % accuracy range