I’ve been interested in repeating the circuits built in the GreatScott video titled “DIY Buck Converter || How to step down DC voltage efficiently” and I came across something that didn’t make sense to me. In the circuit where he uses the Arduino nano to drive a PMOS, he connects the source of the transistor to 12V, then a 10k resistor from source to gate, and finally the gate to a PWM pin on the Arduino. The schematic looks as shown in the attachment.
My question is this, how would the PMOS be turned off (reach cutoff) using this scheme? From my understanding, the voltage difference from gate-to-source (Vgs) would need to be pretty low for cutoff (i.e. around 2V). Wouldn’t a PWM output of 5V make the voltage difference 7V and thus not stop conducting? The only way this would make sense to me otherwise is if the internal circuitry just doesn’t sink current, and so it looks like a high-impedance when on. Is that correct?
(I might have just answered my own question. My theory is that there’s a push-pull output, so when the output for the Arduino is turned high, it refuses to sink current, and thus can block any external voltage incident on it)