Hi! I want to make a 9V to 5V, dc-dc converter circuit using LM7805.I have the schematic attached.

My doubt is how do i make the selection of the capacitors C1 and C2?

I tried simulating with different values like 100nF,10nF and i got the same output of 5V. So how do we select the values of these capacitors?

Regards,
Zaman.

 

The capacitors are there to keep the 7805 from oscillating. They don't affect the DC output voltage.
Use the values recommended in Fig. 10 in the datasheet.

 

C1=.33uF
C2=.1uF
per the datasheet.. The caps are just for noise/stability/transient response.. All of which you probably aren't simulating for.