LT Spice can't simulate this basic mosfet / opamp circuit.

Thread Starter

Luna Tuna

Joined Jan 17, 2019
17
upload_2019-1-20_22-44-0.png

It takes a few minutes to an hour and when it's done it doesn't complete 200 cycles of the PWM, only 1! So it's not working as it usually does. I tried changing the max timestep in the simulation command around. Attached is the schematic in LT Spice form.
 

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Bordodynov

Joined May 20, 2015
2,503
You have an erroneous approach. You placed a floating current source on the diagram! And it is not clear how this will be implemented in reality! You may need a voltage source with a current limited to 10 amperes. It can be done. Also you used standard transistors in the circuit which are very weak. What is the meaning of this?
 

Thread Starter

Luna Tuna

Joined Jan 17, 2019
17
upload_2019-1-20_23-36-13.png


New approach, which seems to be making square waves. So I scrapped the original schematic with 4 mosfets. Does anyone know if I should keep those diodes by the mosfets?
 

Kjeldgaard

Joined Apr 7, 2016
396
In addition to the problem of simulating/implementing the floating current generator, there is a connection dot too much between the left side of the R7 and Gate of the M4.
 

Thread Starter

Luna Tuna

Joined Jan 17, 2019
17
You have an erroneous approach. You placed a floating current source on the diagram! And it is not clear how this will be implemented in reality! You may need a voltage source with a current limited to 10 amperes. It can be done. Also you used standard transistors in the circuit which are very weak. What is the meaning of this?
Thanks. Do you mean my MOSFETs are not high-enough amperage? I thought they were... Anyway this is just a model.
 
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