Can we use analog input pins as a parameter of analogWrite() for PWM?
On the Nano, only the pins D3, D5, D6, D9, D10 and D11 are PWM-capable.
If you try to analogWrite() to any other pin, you will get either
0&nbsp;V (if you write any value less than 128) or 5&nbsp;V (for any
other value).

If you get 3.7&nbsp;V when 5&nbsp;V is expected, that's because either
your power supply is too weak, or you are putting too a heavy load on
the pin.