A display is disclosed that includes a transparent substrate and a plurality of pixel transistors that are formed on the transparent substrate to generate an image for display. A transistor drive circuit is used to drive the pixel transistors to generate the image. The transistor drive circuit may include a gate driver. Further, a test circuit may be used to: adjust voltages that are applied by the gate driver to a pixel transistor; and determine the voltage of the gate driver when a current spike has occurred to the pixel transistor which causes the pixel transistor to turn on. Once this threshold voltage for the gate driver to turn on the pixel transistor has been determined, it may be stored in a storage device for future use by the gate driver. Other embodiments are also described and claimed.