Simulating the MOSFET rectifier

 Before firing up the MOSFET rectifier circuit from yesterday on a breadboard I thought I'd try simulating it with LTspice, here is the schematic:

MOSFET rectifier entered into LTspice

I'm still taking baby steps on LTspice - for some reason I thought it would be time to update  to the latest version.  This really didn't make any difference.

I also had trouble with the simulation and I thought it might be due to the way I was applying the AC to the rectifier.  So a transformer was added using L1 and L2.  I kept the ratio at 1:1 and just fed L1 with 1.414 x 6 V to get the peak input voltage of 8.5 volts.

And I didn't see the TL084 opamp as an option so I selected what appears to be the Linear Technology equivalent (DIP, quad, JFET inputs) LT1058.

At first the circuit did seem to simulate full wave rectification but when I tried adding a capacitor on the output the voltage didn't come up to near the peak as it should with only a string of high value resistors as a load.  So LTspice is seeing a substantial load across the output, possibly the MOSFETs ?

But then I made sure to use models for the transistors called out in the original design and voila, it works (simulates).

MOSFET rectified output (the output below zero needs investigation)

 

A magnification of the peak output of the MOSFET rectifier

Also tried simulating a Schottky diode bridge.  Results weren't quite as good as the MOSFET, about 1/2 volt lower output.

a !n5858 diode bridge

1n5818 bridge output

1n5818 bridge output, peak magnified

  Conventional diodes are worse than the Schottky diodes as far as output voltage.

Silicon diode bridge

Silicon diode bridge output

silicon diode bridge output magnified peak

Now to try the MOSFET rectifier circuit in the real world (and this may take a while as I'm not sure I have the parts other than the TL084).

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm