Looking at the schematic of Adafruit, the screw terminals go directly to the headers. Aka, whatever voltage you supply there will go to the servo's. And most servo's expect 5V.
In the basis there is nothing wrong with using the same supply for both (but keep in mind the voltage as I said above) but keep in mind servo's are hungry little devices! A small servo can draw 1A or more with ease. That might get you in trouble, especially if that power is shared with the Arduino.
Thanks for your reply. When I followed the diagram and wired my components physically, the LEDs on both the PCA and Arduino keeps flickering, and my servos goes crazy. The power keeps getting cut off and on rapidly.
When i connected the USB to the Arduino, then the flickering stops and it works properly.
Does that mean that there is shortage of power to them?
Does that mean that there is shortage of power to them?
No it means you are supplying too much voltage to the servos. You have to feed your board from the 5V output of the Arduino, that maybe not the best of ideas as the Arduino's regulator can not provide enough current.