current source and current mirror design

[chemaphy]

npn current mirror

Hello all, I am now designing a differential resistor ladder that has a top current source and a bottom current source. The current that flows through the resistor ladder is 15mA. I know that for the bottom current source, I can use NPN BJT to generate the current. I also know that I could have used PNP BJT to generate the current source. But since I don't have PNP BJT nor PMOS in my technology, I don't know how to generate the "pull down" current. Can anyone please give me some advice on solving the problem?

Thanks,
chemaphy

 

[DZC]

Maybe you can ask more briefly...

 

[srieda]

If I understand you right, u need a pull-up current... u have a current sink but want a current source.. am I right?

Can u put up a schematic??

 

[laglead]

Can you provide a cirucit schematic.