On the realization of immittance inverters with a minimum number of active components

It is proved that in a grounded 2-port (i.e., a 2-port in which both ports have a common terminal which can be grounded) containing resistors and either one operational amplifier (with differential input and grounded output) or one ideal transistor, the admittance parameters are such that If then , and if then . One consequence of this is that a grounded positive inverter cannot be realized with only one operational amplifier or one ideal transistor (it is known that although the realization of a gyrator requires at least two amplifiers or two transistors, positive inverters can be realized with only one amplifier if only one port is grounded; it is not known whether single-transistor positive inverters are possible). Other consequences concerning the realization of various types of immittance inverters are also discussed.