Voltage-controlled variable oscillator, in particular for phase-lock loops.

摘要

The voltage-controlled oscillator, comprises a differential stage formed by a pair of transistors ( T3 and T4) whose collectors define the output terminals between which an external resonating circuit (LC) is connected. A voltage generator (1) is connected between the two output terminals (A, B) and is suitable for generating a voltage which is proportional to the terminal voltage that exists across the resonating circuit (LC). The voltage generator output signal is applied to the resonation circuit (LC) through a pair of capacitors (Cs) to control the oscillating frequency. A bias current adjustment block (2) varies the bias current (Io) of the differential stage as the operating frequency varies in order to stabilize the peak-to-peak value of the output signal.