switch in charge pump in phase locked loop

[Jalpa Pandya]

in the above circuit there are NMOS and PMOS Current mirror circuits. PMOS SW and NMOS SW blocks represent the mos switches. the W/L ratio for Current mirror circuit is 10/0.18um. the W/L ratio for switches are 2.3/0.18.
If the w/l ratio is increased then the output current provided by the current mirror circuit increases and vice versa. Currently i am getting o/p current of 80ua for reference current of 100ua.

 

[erikl]

This occurs if you have different Vds voltages at your current mirror transistors, s. this image: . Just note the circles!

 

[Jalpa Pandya]

how should i overcome the problem of different vds.

 

[erikl]

Take care (by design) that both mirror transistors have the same Vds. This is possible by control with an OpAmp.