Accurate automatic tuning circuit for bipolar integrated filters

An accurate automatic tuning circuit for tuning the cutoff frequency and Q-factor of high-frequency bipolar filters is presented. The circuit is based on a voltage controlled quadrature oscillator (VCO). The frequency and the RMS (root mean square) amplitude of the oscillator output signal are locked to the frequency and the RMS amplitude of a reference signal, respectively. Special attention is paid to the actual Q-factor in the oscillator. Experimental results for a breadboard circuit operating from 136 to 317 kHz are presented.<<ETX>>

[1]  A. Abidi,et al.  A 12.5 MHz CMOS continuous time bandpass filter , 1989, IEEE International Solid-State Circuits Conference, 1989 ISSCC. Digest of Technical Papers.

[2]  R. Schaumann,et al.  Design and performance of a fully integrated bipolar 10.7-MHz analog bandpass filter , 1986 .

[3]  Takeshi Yanagisawa,et al.  A differential input/output integrator without p-n-p transistors and its application to leapfrog filter synthesis , 1988, 1988., IEEE International Symposium on Circuits and Systems.

[4]  E. Seevinck,et al.  Transconductor and integrator circuits for integrated bipolar video frequency filters , 1989, IEEE International Symposium on Circuits and Systems,.

[5]  Takeshi Yanagisawa,et al.  A monolithic video frequency filter using NIC-based gyrators , 1987, 1987 Symposium on VLSI Circuits.