I am using a 555 timer and an NPN transistor to drive an array of 12 LEDs from a 9v battery, and a potentiometer to control the duty cycle. I am concerned about the voltages the LEDs will be subjected to during the transistor's on/off transitions.
My simulated circuits:
I understand that when the transistor is off, having 9v on the anode side of the LEDs is fine because there's no path to ground. Likewise, when the transistor is fully on, an operating voltage of just over 3 volts for my LEDs is fine. But real transistors won't transition between on and off instantaneously, so how can I protect my LEDs from voltage spikes that will either destroy them or wear them out faster? Is it even necessary for this circuit?