Circuit arrangement for avoiding parasitic oscillation modes within an oscillator circuit

摘要

Harmonic oscillators normally comprise an integrated amplifier and an external LC resonant circuit. The frequency-selective nature of the LC resonant circuit results in harmonic oscillators having a better phase noise than multivibrators. However, it is disadvantageous that inductance and variable-capacitance diodes are difficult to integrate and that the LC resonant circuit generally has to be external. The parasitic elements of the housing, such as inductance of the bonding wire or capacitance of the connecting pins, which are thus between the integrated amplifier and external LC resonant circuit, can lead to parasitic radio-frequency oscillation modes. The invention is based on the object of reducing these interfering influences. In the circuit according to the invention, the reduction of interfering influences in an LC resonant circuit with an integrated circuit is effected by including the interfering elements of the housing in the resonant circuit. This precludes the occurrence of parasitic radio-frequency oscillation modes. It also ensures good radio-frequency properties and a wide frequency tuning range.