Negative impedance converter

The negative impedance converter (NIC) is a one-port op-amp circuit acting as a negative load which injects energy into circuits in contrast to an ordinary load that consumes energy from them. This is achieved by adding or subtracting excessive varying voltage in series to the voltage drop across an equivalent positive impedance. This reverses the voltage polarity or the current direction of the port and introduces a phase shift of 180° (inversion) between the voltage and the current for any signal generator. The two versions obtained are accordingly a negative impedance converter with voltage inversion (VNIC) and a negative impedance converter with current inversion (INIC). The basic circuit of an INIC and its analysis is shown below. The negative impedance converter (NIC) is a one-port op-amp circuit acting as a negative load which injects energy into circuits in contrast to an ordinary load that consumes energy from them. This is achieved by adding or subtracting excessive varying voltage in series to the voltage drop across an equivalent positive impedance. This reverses the voltage polarity or the current direction of the port and introduces a phase shift of 180° (inversion) between the voltage and the current for any signal generator. The two versions obtained are accordingly a negative impedance converter with voltage inversion (VNIC) and a negative impedance converter with current inversion (INIC). The basic circuit of an INIC and its analysis is shown below. INIC is a non-inverting amplifier (the op-amp and the voltage divider R 1 {displaystyle R_{1}} , R 2 {displaystyle R_{2}} on the figure) with a resistor ( R 3 {displaystyle R_{3}} ) connected between its output and input. The op-amp output voltage is The current going from the operational amplifier output through resistor R 3 {displaystyle R_{3}} toward the source V S {displaystyle V_{ ext{S}}} is − I S {displaystyle -I_{ ext{S}}} , and So the input V S {displaystyle V_{ ext{S}}} experiences an opposing current − I S {displaystyle -I_{ ext{S}}} that is proportional to V S {displaystyle V_{ ext{S}}} , and the circuit acts like a resistor with negative resistance In general, elements R 1 {displaystyle R_{1}} , R 2 {displaystyle R_{2}} , and R 3 {displaystyle R_{3}} need not be pure resistances (i.e., they may be capacitors, inductors, or impedance networks).