At least one N-type transistor and at least one P-type transistor separate from the digital circuit are sized to represent the total area of the corresponding type transistors in the digital circuit. The gates of the N-type transistor and P-type transistors are set to voltages according to the corresponding off-state logic levels of the digital circuit. The N-type and P-type transistors form a portion of corresponding current mirror circuits, which can provide outputs to a leakage current monitor and/or a control circuit such as a comparator that determines when leakage current for the N-type or P-type devices has exceeded a threshold. The output of the measurement/control circuit can be used to determine a temperature of and/or control operation of the digital circuit or the system environment of the integrated circuit.