Negative resistance models the required gain needed from the active network to sustain stable oscillations. The negative
resistance model is shown in the figure below. The crystal is represented by a reactance term Xm and a motional resistance term Rm. One process used as a means to easily evaluate the negative resistance characteristics and oscillation allowance of an oscillator circuits is the method of adding a resistor to the hot terminal of the crystal unit and observing whether it can oscillate (examining the negative resistance). The oscillator circuit capacity can be examined by changing the value of the added resistance. Refer to application note AN-802 for more details. For other questions not addressed by the Knowledge Base, please submit a technical support request.