Background: I'm using a NPN transistor (TIP-122) to switch power (digital, with PWM) to a ceramic resistor/heater. I'm trying to finalize the circuit and move it from breadboard to perfboard. I will want to periodically swap the heater. One heating element draws 0.58A (at 12V), the other will draw 5A (at 5V).
If I choose a resistor for the base such that the transistor is saturated and applying enough current for the high power heater, will it cause damage when used with a lower power output? Or is the base resistor only present to protect the signal input (which is only designed to supply a tiny current)?