Patent ID: 6140884
Filing Date: 2000-10-31
Classification: H03B

Abstract:
An integrated circuit for a voltage controlled oscillator (VCO) comprising:first and second ports (Port 1, Port 2) for connection to an external resonator (L.sub.1, D.sub.1, C.sub.p, L.sub.p),first and second transistors (T.sub.1, T.sub.2) each having first and second controlled electrodes and a control electrode,the first transistor (T.sub.1) having its first controlled electrode coupled via a filter (C.sub.f, L.sub.f) to the first port (Port 1), the resonant frequency of the filter being within the intended frequency range of the VCO,the second transistor (T.sub.2) having its first controlled electrode coupled to the second port (Port 2),means (C.sub.1) for AC coupling the first controlled electrode of the first transistor (T.sub.1) to the control electrode of the second transistor (T.sub.2),the second controlled electrodes of the first and second transistors being coupled together and fed by a current source (I.sub.1), andmeans (C.sub.3) for decoupling the control electrode of the first transistor, wherein, in operation, negative impedance is exhibited between the first and second ports.