The present invention relates to circuits and methods for detecting transistor operation in the triode region including a circuit for a transistor in a constant current source. The circuit comprises a detector having a first input, a second input, and an output. The first input of the detector is coupled to the source of the transistor and the second input of the detector is coupled to the set point terminal of the constant current source. The circuit also comprises a flag coupled to the detector output. The detector has parameters selected so that, when the voltage at the source of the transistor satisfies a reference condition, the output of the detector sets the flag. The reference condition is established relative to the voltage at the set point terminal of the constant current source and relative to the triode transition voltage of the transistor at a selected drain-source current.