constant current reference

[caosl]

hi,all
I need a constant 50nA current reference in my project , but now,i encounter some trouble with it, appreciate all you advice, thanks very much!

 

[Miguel Gaspar]

What kind of current source you need. DIscrete or with op-amp.

Please let me know

 

[pfd001]

How about the temperature coefficent

 

[caosl]

How about the temperature coefficent

first, Thanks to your reply!!
without opamp, just a current reference,keep constant value over the full power supply,the traditioal cnstant gm circuit seems not a good choice , moreover, over the range of -40-125 temperature,it's value change less than 5nA, is there any method to deal wuth this problem?

 

[jjsnail]

the TC=5/(50*165)=606ppm

I have ever done a current reference ,its TC was about 500ppm,but it woks on 2u current .

 

[pfd001]

It seems that your design is challenge. I am not sure that the spice model is accurate when the transistor work in so low current region.