Um, brightness isn't what I am after. Controlling it's output level is also not what I seek from the LED. When I turn it on, I want the voltage to increase at a fixed rate until it reaches peak voltage, then stay there, making the LED light up like a filament bulb. Take a halogen lamp for example. Turn it on, and it takes at least two milliseconds to reach maximum output. When you turn it off, as the heat dissipates from the filament, the light output takes up to four milliseconds to completely diminish. This is the effect I want to achieve when turning on and off an LED.