Controllable oscillator having transconductance circuits with amplitude stabilization

摘要

Controllable oscillator circuit comprising a regenerative loop which incorporates a cascade circuit of first and second sections each having a controllable gain and a phase shift which is 90° at the oscillation frequency, and an amplitude detection arrangement which is coupled between an output and a control input of at least one of the two sections. To obtain a comparatively large tuning control range and an effective amplitude stabilization, the two sections are mutually substantially equal and the first and second sections comprise first and second controllable transconductance circuits, respectively, outputs of which are coupled to third and fourth controllable transconductance circuits which are positively fed back from the output to the input, and which are coupled to first and second parallel RC filters and to inputs of the second and first controllable transconductance circuits, respectively, control inputs of the first and second transconductance circuits being coupled to a tuning control input and the output of at least one of the two first and second transconductance circuits being coupled to control inputs of the third and fourth transconductance circuits via the amplitude detection arrangement.