If you are using a mosfet as a switch, you need a pulldown resistor to discharge the gate or it may not turn off.
However, if you are activating a mosfet via an output pin HIGH or LOW, do you need a pulldown resistor, or will the pin at LOW discharge the gate?
Yes, for example to prevent the floating state of the pin when controller is off or during the startup procedure.
Thanks for clarifying that.
However, if the pin connected to the MOSFET gate is not a microcontroller pin, but an output pin from an ordinary logic chip like 74hc595 (with OE connected to ground) then that pin will not float at startup, so no pulldown resistor would be needed.
A chip like 74hc595 starts up with all outputs LOW. But if it's inputs are connected to microcontroller pins, which do float at startup, this can cause the the chip's input pins to receive random data, causing its's output pins to also output random data. This can be prevented by connecting pulldown or pull-up resistors to the chip's input pins. In the example of 74hc595, a pulldown resistor on the serial input, clock or latch pins should prevent any random data being clocked or latched into the chip while the microcontroller is starting up.
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