Hi all,
I am currently working on a project which is able to generate three phase signal, using a microcontroller Teensy++2.0 and MOSFET circuits. The MOSFET circuit will be able to convert/smoothen the square waves with variable duty cycles generated by the microcontroller into reasonable sine waves. To begin, I started with a single phase.

NI MultiSim is used as the simulation tool, and for that purpose opamp together with sine wave and triangular wave generator replaced the microcontroller to generate the required square waves for testing purposes.

Objective: To get a reasonable looking sine wave
After weeks of trying and troubleshooting, I am still unable to get the required output (reasonable looking sine wave).

My circuit design is shown below: (Left shows the function gen used) (Mid is the circuit) (right is the output that I generated)


I would appreciate your advice and guidance.
Please help.

Thank you so much.
KX

 

Welcome to AAC!
The IRF840 has a Vgs(thr) that can be as high as 4V, but to turn fully on needs a Vgs of 10V or so. That means Vg should be pulled up to Vdd+10V = 19V. Your circuit cannot do that. Have you considered using a "high side MOSFET driver" IC?