[![enter image description here](https://i.stack.imgur.com/ir01N.png)](https://i.stack.imgur.com/ir01N.png)

I'm having some troubles with this simple circuit where Vi is a sinusoidal signal.

If you consider that the initial voltage across the capacitor is 0 V, then until Vi reaches 0,7 V the diode behaves as an open circuit. When Vi reaches 0.7 V then V1 = Vi - 0.7 V. At this point, there will be a current which flows through the resistor and which charges the capacitor.

But I can't find a simple way to determine the voltage drop across the resistor and the capacitor, I should solve a differential equation. As a consequence I can't figure out when and if the diode will behave as a closed circuit again.

In the particular case where the value of the resistance is negligible and the voltage drop across the resistor is negligible too, I would say that Vo should stay at the constant value of Vi(max) - 0.7 V (the diode remains an open circuit).

I hope that someone could explain a fast and simple method to deal with this circuit and determine the signal Vo(t).