Question

What is the phenomenon of differential negative resistance (negative differential resistance) and how can it be used in electronic devices? Please explain it in two or three paragraphs

Answer 1

Negative resistance is a property of some electrical circuits and devices in which an increase in voltage across the device's terminals results in a decrease in electric current through it.

In a device or circuit with negative differential resistance (NDR), in some part of the I–V curve the current decreases as the voltage increases

The I–V curve is nonmonotonic (having peaks and troughs) with regions of negative slope representing negative differential resistance.

Negative differential resistance

Voltage controlled (N type)

Current controlled (S type)

Passive negative differential resistances have positive static resistance; they consume net power. Therefore, the I–V curve is confined to the 1st and 3rd quadrants of the graph, and passes through the origin. This requirement means (excluding some asymptotic cases) that the region(s) of negative resistance must be limited, and surrounded by regions of positive resistance, and cannot include the origin.

Amplification

A negative differential resistance device can amplify an AC signal applied to it. if the signal is biased with a DC voltage or current to lie within the negative resistance region of its I–V curve.

Explanation of power gain

The diagrams illustrate how a biased negative differential resistance device can increase the power of a signal applied to it, amplifying it, although it only has two terminals. Due to the superposition principle the voltage and current at the device's terminals can be divided into a DC bias component ({\displaystyle V_{bias},\;I_{bias}}) and an AC component ({\displaystyle \Delta v,\;\Delta i}).

Reflection coefficient

The reason that the output signal can leave a negative resistance through the same port that the input signal enters is that from transmission line theory, the AC voltage or current at the terminals of a component can be divided into two oppositely moving waves, the incident wave {\displaystyle V_{I}\,}, which travels toward the device, and the reflected wave{\displaystyle V_{R}\,}, which travels away from the device.