MOSFET rectifying circuit

[raff5184]

Hi all,

I tried to make the MOSFET rectifier in the attached image. The input is a 1MHz sinusoid varying from 5Vpp to 20Vpp coming from a signal generator followed by amplifier.

The circuit for some reason doesn't work. This is what I observed:
the moment I connect the input to the circuit, the input sinusoid gets "randomly" shifted up or down, and/or its amplitude becomes much smaller, the output on the other hand is always 0 Vdc. In a couple of occasions, the input wasn't shifted and I could see the rectified output but it lasted for few seconds, as it was unstable, and then the same behavior.

I tried two combinations of MOSFETS:
A) Two N-ch DMN65D8L  and two P-ch DMP3098LDM
B) Two N-ch XP231N02013R-G and two P-ch ZXMP3A17E6TA

Might it be because of some imbalance in the circuit, like the current flows only in one side and not in the other? Maybe because the FETs are not exactly of the same series? And so it can't switch properly?

[klr5205]

Difference in turn-on time causing shoot-through perhaps?

[Ice-Tea]

Probing technique? Very easy to short out your circuit with a scope like this. Recommended viewing material:

[raff5184]

I eventually removed the scope probes and I only have an amperometer in series to the load (a capacitor)

[Zero999]

I eventually removed the scope probes and I only have an amperometer in series to the load (a capacitor)

There's your problem: that circuit is unsuitable for capacitive loads.

[raff5184]

that was a quick solution   
Just out of curiosity and to learn, why is it?

[Zero999]

that was a quick solution   
Just out of curiosity and to learn, why is it?

I suggest you try to figure it out for yourself. Assume the MOSFETs have a threshold voltage of 2V and they have a body diode, in reverse parallel with the drain and source. Note the gate-source voltages, when the sine wave is at the peak positive and negative extents, without a capacitor on the output. Now do the same, with the capacitor on the out. If that doesn't help, try simulating it. If you don't want to install a program, such as LTSpcie, then use the online simulator linked below:
https://www.falstad.com/circuit/

To use a MOSFET regulator, to drive a capacitive load, add a Shotky diode to the output, or use a MOSFET bridge rectifier controller IC.

[raff5184]

Great Zero,
will try that, thanks