How to realize the voltage reference?

[Adam2008]

how to realize a current source

Hi,

I am developing a charge pump PLL. If I am using the charge pump circuit in Razavi's book. how can I realize the two gate voltage of the current sources? Shall I use voltage reference?

Thank you.

 

[safwatonline]

use a bias current generator
i.e. current is generated from bias cell then mirrored to the CP

 

[Adam2008]

Thanks.

Could you give more detail about the bias current generator?

 

[jecyhale]

Hi,

I am developing a charge pump PLL. If I am using the charge pump circuit in Razavi's book. how can I realize the two gate voltage of the current sources? Shall I use voltage reference?

Thank you.

NO, gate voltage is detemined by the Id of it. You should design current bisa. After you have a constant (some range) current, use current mirror as the current source.