Amplitude controlled sine wave oscillator

摘要

An amplitude control circuit of the invention includes a vector composition circuit (18) for composing a cosine-wave signal (e3) from a sine-wave signal (e1) and a control signal generation circuit (20) for providing a control signal (e4) from the sine- and cosine-wave signals (e1, e3) which the control signal (e4) has substantially no ripples. DC level of the control signal (e4) is varied proportional to the amplitude of the sine-wave signal (e1) regardless of the frequency of the sine-wave signal (e1). The amplitude of an amplification control circuit (12) is controlled by the control signal (e4) so that the amplitude of the oscillation output signal (e1) derived from the oscillation circuit (16) is constant.