The question asks to create an equation for the time delay for the LED to turn off in terms of capacitance(CT), reverse current (IL) of the 1N4148 and the threshold voltage (Vt) of the MOSFET for the circuit below.
The hint given was that we can treat the 1N4148 as a current source with a value of 2 nA.
From the experiment that I performed, Threshold voltage = 1.824 V, Capacitance = 0.01uF, resistance = 600Ω, yield the LED turn off after 8.71 seconds.
I feel like I would use the capacitor equation, i=C dv/dt, solving for dt, and plug in the values above. Is this a step in the right direction to solve this question.