Current controlled variable frequency oscillator having an improved operational transconductance amplifier

摘要

A current controlled variable frequency oscillator (260) operates at a characteristic frequency that is determined primarily by a scaled current. A filter cascade (320) receives the scaled current for setting a filter cascade frequency substantially equal to the characteristic frequency. Additionally, the filter cascade (320) receives a triangular signal at a non-inverting input, the filter cascade (320) converting the triangular signal into a sinewave signal. A lowpass filter (330) receives the scaled current for setting a lowpass filter frequency to a frequency substantially less than the characteristic frequency. The lowpass filter (330) also receives the sinewave signal and provides an average signal therefrom. A comparator (340) receives the scaled current, wherein the comparator (340) compares the sinewave signal and the average signal for providing a substantially squarewave signal therefrom. An integrator (310) is provided for receiving the scaled current, the integrator (310) integrating the substantially squarewave signal for providing the triangular signal therefrom.