Accurate automatic tuning circuit for bipolar integrated filters

I n this paper an accurate automatic tuning circuit, for tuning the cut-off frequency and Q-factor of high frequency bipolar filters, is presented. The circuit is based on a voltage controlled quadrature oscillator (VCO), IS presented. The frequency and the RMS amplitude of the oscillator output signal are locked to the frequency and the RMS amplitude of a reference signal res ectively. Special attention is paid to the:ictual Q-pact or in the oscillator. Experimental results of a breadboard circuit operating from 136 to 317 kHz arc presented. Eventually the circuit will be scaled up iii requency and integrated for on-chip tuning of bipolar video frequency filters