hi,
there is a question. to design proper drive I implement a very simple circuit. I turn on a DC lamp with a MOSFET. why when I reduce gate resistor ( from 120ohm to 18ohm), the mosfet does not get fully saturated and the lamp turn on with reduced light and mosfet gets hot. obviously it work in active region. why? , while with reduced gate resistor it must be get saturated rapidly.
I would be appreciated if you reply to my question.
I guess you managed to build an oscillator. This can happen if the circuit has large source inductance, e.g. on a breadboard. In this case a large gate resistor is helpful to stop oscillations.