When the switch 104 closes, an electrical connection is created between the common voltage 110 and the first reference voltage 112. This causes current from current source 102 to transmit through the LED 103 causing light to emit from the sub-pixel 72. Thus, emission periods of the sub-pixel 72 may be varied to control a perceived light emitted from the sub-pixel 72 through changing a number indicated by the image data 98. Additionally or alternatively, in some embodiments, the second reference voltage 114 is included to alter an overall current value used to control light emitted from the LED 103. For instance, the second reference voltage 114 may increase a sensitivity of the LED 103 to current changes such that a lower current value may be used to cause light to emit from the LED 103, or used to enable the LED 103.