Negative resistance

Negative resistance is an electrical behavior in which current decreases as voltage increases over some operating range. It can arise from nonlinear devices and is distinct from ordinary positive resistance.

Negative differential resistance: A region of a device’s current–voltage curve where increasing voltage decreases current. This is the precise small-signal behavior behind the voltage-driven decrease in current.
Electronic oscillator: A circuit that produces a periodic electrical signal from a power supply. Negative resistance can compensate circuit losses and sustain oscillation.
Ohm's law: The relation between voltage, current, and resistance in an ideal ohmic conductor. Its positive, constant resistance provides the baseline that nonlinear negative-resistance devices depart from.
Positive resistance: Electrical resistance in which current increases with voltage under the stated operating conditions. It has the opposite current response from the behavior defined here.
Current–voltage characteristic: A curve or relation showing the current through a device as a function of applied voltage. Negative resistance appears as a negative-slope segment of this curve.
Microwave oscillator: An oscillator that generates electromagnetic signals at microwave frequencies. Gunn and tunnel devices use negative differential resistance to generate microwave power.
Differential resistance: The local slope of voltage with respect to current at an operating point. Its sign specifies the incremental response, which may differ from a device’s static resistance.
Negative resistance converter: An active circuit that presents a negative input resistance at its terminals. It synthesizes negative resistance through feedback rather than relying on a device’s intrinsic curve.
Tunnel diode: A heavily doped semiconductor diode whose quantum tunneling produces a region of negative differential resistance. Its tunneling current falls as voltage rises across a useful operating interval.
Relaxation oscillator: An oscillator that produces repetitive waveforms by switching between charging and discharging states. Negative-resistance switching can trigger repeated transitions in relaxation circuits.

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