3KHz is a very small BW, which will need bulky resistors and capacitors.
Try to read National Application Note AN1001, then write ur MATLAB code. From this code u will have the elements values which u will begin design, then try to dec the cap and watch the PM and the phase noise, till u reach the best solution. If the cap is still big, try to use gate capacitance (in order to get use of its large density)
What is the calculated value of the cap, and will u use a 2nd or 3rd order filter ??