Negative Differential Resistance Effects

The negative differential resistance (NDR) condition is shown by some materials under proper circumstances further more. In some device components, at a given interval of applied voltage, the slope of the I/V curve becomes negative. It is straightforward that the definition of negative resistance is only related to the differential resistance $$\frac{dV}{dI}$$ , the value of the resistance ( $$\frac{V}{I}$$ ) being always positive.