I am trying to generate a 65V square wave very similar to the post found here: Mosfet PWM signal not square
My load is in a slightly different configuration (I've tried them both ways), but the problem I am having is very similar to the original poster in the link above.
Basically I'm switching a FET that is in connected to a 65VDC supply through a 10K resistor and placing my load across the FET. Here is my circuit:
Here are my scope shots; the blue is voltage across the load and the yellow is the gate signal:
I'm inquiring how I can make that rising edge across the load fast and sharp. The rounded edge makes me unable to achieve 65V when I increase the switching frequency since the capacitance in the load and my resistor cause the voltage across the load to rise too slowly. The screenshots show about a 60Hz frequency, but I'd like to get up to about 10kHz.
My load is a PLDC diffusing film and there is about 1μF worth of parasitic capacitance built into the material which I cannot remove. I am also aware that I can reduce the 10kΩ ohm resistor at the drain of the FET, but since my peak voltage is 65V, reducing the resistor begins to put quite a bit of power on that resistor which I'd like to avoid.
The only other way I can think of to make this happen is by putting another FET in parallel with the drain resistor and syncing and inverting the gate signal of this other FET such that it will turn on when the other one turns off and vice versa.
But is there a better way than this?
I tried putting the load in place of the 10kΩ resistor with the voltage developing across the load being less. In regards to the FET not being turned on completely, I am using a frequency generator and have increased the turn-on voltage to 10V with no different results so I don't think that is the issue, see my scope shots below. Yellow is the gate drive, blue is the voltage across the FET, purple is the high (65V), and red is the voltage across the load.