Multi-band voltage controlled oscillator in which unnecessary circuit parasitics can be avoided

摘要

In a voltage controlled oscillator in which an operation frequency is determined by applying a tuning voltage to a resonant circuit connected to a control terminal of a transistor (T1), the resonant circuit has zeroth and first varactor diodes (D0, D1) which can serve as capacitance elements. A selection voltage is applied to an anode of the first varactor diode through a band selection terminal (1). The first vatactor diode has a capacitance varying in response to the value of the selection voltage. The variation of the capacitance causes a change of a frequency band of the voltage controlled oscillator. A tuning voltage is applied through a tuning terminal (2).