Negative impedance converter

A negative impedance converter is an active circuit that presents an input impedance equal to the negative of a connected load’s impedance. It uses powered amplification and feedback to make voltage and current at its input behave as though the load’s impedance had reversed sign.

Voltage inversion: A circuit operation that reverses a signal’s polarity while preserving its magnitude, ideally. The voltage-inversion topology uses an inverted voltage to create negative input resistance.
Electrical impedance: The frequency-dependent opposition a circuit presents to alternating current, combining resistance and reactance. The converter acts on this ratio between voltage and current.
Negative capacitance: An effective circuit behavior whose voltage-current relation corresponds to capacitance with a negative value. A negative impedance converter can synthesize negative capacitance to offset positive capacitance.
Passive network: A circuit network that cannot generate net energy and contains no active power source. A negative impedance converter uses external power and can deliver energy to its load.
Current inversion: A circuit operation that reverses current direction while preserving its magnitude, ideally. The current-inversion topology produces negative impedance through a different feedback arrangement.
Negative resistance: An electrical behavior in which current decreases as voltage increases over some operating range. Negative resistance is the simplest case of the negative impedance the circuit can present.
Negative inductance: An effective circuit behavior whose voltage-current relation corresponds to inductance with a negative value. Impedance inversion can synthesize negative inductance without a physical inductor of negative value.
Positive resistance: Resistance for which voltage and current have the same sign under the passive sign convention. Ordinary positive resistance dissipates energy, whereas negative resistance can supply it.
Operational amplifier: A high-gain differential voltage amplifier commonly used with external feedback to implement analog circuits. Operational amplifiers provide the gain and feedback used in many negative impedance converters.
Reactance: The frequency-dependent opposition to alternating current contributed by capacitance and inductance. A converter can invert reactive as well as resistive parts of a load.

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GyratorCompared with: Both circuits transform impedances, but a gyrator creates a cross-port inverse rather than a negative impedance.