Some Gyrator and Impedance Inverter Circuits

The use of feedback amplifiers to provide impedance inversion is considered. If the proper types of feedback connections are used, and the input and output impedances of the amplifier and its gain are chosen suitably, the input impedance of the circuit will be approximately proportional to the reciprocal of the load impedance. The approximation may be improved by the insertion of negative impedance elements to compensate for the residual impedances in the inverter. When this is done, the circuit exhibits gyrator properties. Experimental verification of one of the circuits, using high quality stable amplifiers, gave a range of impedance inversion of two decades.