Measuring output voltage for rectifier with filter

shaikss

I need your help in understanding the concept.
Actually, I am trying to understand the grounding concept here:

Attached is the snapshot:
Hi Folks,

I need your help in understanding the concept of how to measure the output voltage.



1. Initially, I tried to monitor the voltage between the drain of PMOS(Vh) and drain of NMOS(Vl). Since there is no cap and no resistor, I observed ripple.
Second attachment is the output of the same.

2. Then I connected a cap in between net 'vh' and net 'vl'. Then I observed a drop down in the voltage as shown in third file.
3. Out of my curiosity and to cross-check how grounding impacts: I have conducted below experiment:

I connected one end of cap of 1pf and res of 100K to Vh and the other end of cap and res are grounded. I measured the output between Vh and Vl. As expected, I observed the output as in case 1.

4. I grounded Vl (which shouldn't be case) and grounded one end of cap and res to ground while the other end is being connected to Vh. I observed output across resistor. Fourth file is attached for its output. In this attached file, there are two plots. The plot with lower voltage is the one I have observed when I measured the voltage across resistor when it is grounded and Vl is not grounded.

5. Later on, from my experiment 2, I realized that the voltage is drooping down. So, I increased the time scale and then checked how its actually going on. I observed some interesting results. Fifth file is attached.

Can you explain me why it is happening so?

If I go for N-stage rectifier, the Vl of first stage is always grounded.
So, is it good practice to do so.

Please clarify my querie

Attached Thumbnails

     

Kholdstare

Most obvious answer would be the output(s) is where no bias signal is connected.