Amplitude-controlled harmonic oscillator - has detector with logarithmic characteristic to measure output signal amplitude

摘要

The amplitude-controlled oscillator has a linear amplifier and passive resonant circuit forming a closed loop. The amplitude is stabilised by a control circuit comprising an amplitude detector, a comparator, a controller and a device to set the loop gain. The detector that measures the signals amplitude has a logarithmic transfer characteristics and consists of a linear amplitude converter coupled to a logarithmic transformation circuit. The transformation circuit comprises an amplifier with a common base transistor in its negative feedback loop.