| 摘要 |
An active inductor circuit includes a primary and a secondary coil and a drive circuit, all of which are monolithically integrated on a common substrate to provide high-Q inductors, which can in turn be used to provide high performance resonators and filters. Each active inductor circuit comprises a primary coil which carries a first current that varies with an RF input signal, and a secondary coil which carries a second current that also varies with the input signal; an on-chip current source provides the second current. The inductor circuit is arranged such that there is a fixed phase difference of approximately 90° between the first and second currents, and such that the magnetic field induced by the second current compensates for energy that would otherwise be dissipated by the primary coil. When the second current is properly selected, the inductor circuit's input impedance is made purely imaginary, such that the circuit emulates an ideal inductor at a particular frequency. The inductor coils and current source are fabricated on a common substrate, with the current source preferably using CMOS components. The present active inductor circuit can be combined with on-chip capacitors to form fully integrated high performance resonators and filters, using mainstream fabrication techniques.
|
