Abstract: A method and apparatus to provide performance adjustments for FEDs during operation are provided. More specifically, the present invention provides two circuit embodiments for compensating for temperature induced brightness variations of the panel display. In a closed loop embodiment, a sample display circuit that is substantially similar to a FED being adjusted is used to generate a performance indicator signal which is compared against a reference signal to determine a difference signal. The difference signal is then used to adjust the operation performance of the FED as well as the sample display circuit. In an open loop embodiment, a current source generates a reference current across a sample resistor which is made from the same material as the resistor layer inside the FED's cathode. The voltage across the sample resistor is compared against a reference signal to determine a difference signal.