Negative resistance has temperature dependent, and changes depending on the operating environment temperature.

The tendency generally decreases linearly from low temperature to high temperature (see the graph below), and the slope differs depending on the circuit (IC, crystal unit, etc.).

For this reason, the temperature characteristic of negative resistance is measured at three points: the minimum temperature, the normal temperature and the maximum temperature within the operating environment temperature range specified by the customer.

The negative resistance temperature characteristic result is judged based on whether or not the lowest measured value (in many cases, the high temperature side) of the three measured negative resistance values exceeds the negative resistance target value.