New non-gyrator type active inductors with applications

Active inductors based on a floating capacitor connected between two controlled current sources are considered. The first source controlled by the circuit input voltage supplies a current to the capacitor and develops the voltage on the capacitor shifted by 90° degrees with respect to this first current. This capacitor voltage is controlling the second current source, and due to this last control the circuit input current, besides inductive, has an active component. If a third current source also controlled by the input voltage compensates the active component then the current seen by the input voltage source becomes purely inductive. This simplified model allows one to obtain new realizations of active inductors and improve control of the inductance Q-factor. In the well-known active inductor the compensation is achieved by addition of one transistor only to the existing circuit. The overcompensation results in a very low power inductor-less oscillator. The examples of realization for 2 to 5 GHz range are given.