I'm playing around with Mosfet switches in LTspice and trying to get one working which should switch relatively high frequency PWM signals from 1- 150 Khz.
My supply voltage is (-)80 V, the Mosfet I'm using is a P-channel enhancement type IRFP9240, RGate is 10 kOhms, the pull down resistor is 10 kOhms and RLoad is 100 kOhms.
The switch works fine for a 1 Khz 50% duty cycle PWM signal and the waveform/amplitude at the output is also ok, but at higher frequencies like 50 Khz 50% (PWM) the signal at the Output gets completely distorted and the amplitude goes from
(-)3 V - (-)17 V, at 80 Khz 50% duty cycle (PWM) the same thing happens but even worse.
I read the Mosfets datasheet and the mosfet should be able to handle these frequencies without problems I think.
The Mosfets VTh is (-)2 V, (-)10 V are required to fully turn the Mosfet on, the maximum VGS is (-)20 V so I'm using (-)12 V at the gate.
I've tried everything with different values without any success, I just cant get it working at higher frequencies.
The pictures show the output at 50Khz 50% duty cycle PWM and the input PWM signal.
I don't know what I'm missing or doing wrong.
Help would be appreciated.
50Khz 50% duty cycle pwm pulse source : PULSE(0 -12 0 0 0 0.01m 0.02m)
80Khz 50% duty cycle pwm pulse source : PULSE(0 -10 0 0 0 0.00625m 0.0125m)