Negative resistance is the ability of the circuit to cancel out the resistance RL of the crystal unit and oscillate, but this alone does not lead to the stable oscillation. Since the resistance RL of the crystal unit at start-up is larger than the resistance value at steady state, only RL is insufficient for the negative resistance value.
Therefore, it is necessary to have a sufficient margin to prevent startup failure and ensure stable oscillation startup.

For this reason, NDK sets a recommended negative resistance value based on our own calculation, which takes into account a sufficient margin.
We investigated the correlation between the oscillation start and the electrical constants (R1, C1, L1, C0) of the crystal unit, and derived the relationship between these values.
However, this is only a target value, and for customers who have a negative resistance standard, we conduct circuit analysis taking that value into consideration.