An LED can be driven from a voltage source by connecting it in series with a resistor. In this case, the difference between the source voltage and the forward bias voltage is the voltage drop across the series resistor. The forward bias current through the LED is set by the size of the resistor. This method has the advantage of dissipating the heat outside the voltage-source device, in the series resistor. Therefore, the voltage-source device is insensitive to heat dissipation and is good for driving multiple LEDs in series with different forward-bias voltages (VF) from the same supply. Alternatively, a current-regulated source may be used to drive an LED. This results in the LED light remaining constant, even when the supply-voltage fluctuates. Last, a DC/DC converter can be used to regulate the LED current but this method has the disadvantage of increased cost.