The Analysis And Design Of Active Inductor

As one of the most basic components in the circuit,the inductor can not only constitute the frequency selection network with capacitance,but also used in the various RF modules(filters,low noise amplifiers,power amplifiers,mixers,voltage controlled oscillators,etc.)of the radio transceiver,with the realization of impedance conversion,feedback,tuning,filtering and other functions.Because the role of the inductor is very important,the research on the inductor is essential.With the increasingly miniaturizetion of integrated circuits,the parameter characteristics of Inductance can not meet the requirements of using in its size and quality factor when integrated.So people study the active inductance to solve the contradiction between the size and the quality factor of the passive inductor.The so-called active inductor,is composed of active devices,resistors and capacitors.The active network can be divided into two categories according to the working principle,the feedback amplifier type and the impedance converter type.Most of the researches on active inductors are based on impedance converter types.The key to designing active inductive circuits is the gyrator.The ideal gyrator is a two-port network with an inverted characteristic.Inverse characteristics can turn a capacitor back into an inductor or turn an inductor into a capacitor.When the input is a sinusoidal voltage,the load impedance is a capacitive element,the rotator converts the capacitor into an inductor,called an equivalent inductance.In this paper,the active inductor circuit based on the operational amplifier and the active inductor based on the transistor-based active inductor are designed to use the reversal characteristic of the gyrator.Inductance value from the cents to Henry level based on the op amp’s active inductor circuit,the resistance can reach tens of ohms to several thousand euros;in the quality of the inductor,the active inductance is closer to the ideal component than the general inductor and is applied to the low frequency circuit.If the active inductance circuit needs to be applied to a higher operating frequency,the op amp’s gain bandwidth has been difficult to meet the circuit design requirements.As the frequency increases further,the gain drastically decreases and the noise of the circuit deteriorates gradually.It is difficult to apply to high-frequency,with the traditional operational design of the active amplifier.It is well known that transistors can be used not only as amplifiers,but also at very high operating frequencies.Therefore,this paper also studies the active inductance based on transistor composition.The basic principle of the design circuit is to use the inverse function of the gyrator to turn the intrinsic capacitance of the transistor into an inductor.The circuit with a transistor instead of a conventional op amp can be designed to operate at a megahertz or even gigahertz frequency.The transistor design circuit has two advantages: the transistor gain bandwidth is very large,its characteristic frequency can be very high,can meet the needs of high frequency;its noise and power consumption is much lower than the amplifier.After designing the active inductor,the inductance constitutes the resonant circuit with capacitor,measures its gain and phase,and simulates its S parameter.It not only verifies that the designed circuit can be equivalent to the inductance,but also apply it to the resonant network.