AUTOMATIC TUNING SYSTEM FOR INTEGRATOR-BASED CONTINUOUS-TIME FILTERS

This paper proposes an automatic tuning system to adjust frequency cha racteristics of integrated continuous-time filters especially at high frequencies. Frequency characteristic deterioration of a filter using integrators with electrically controllable unity-gain frequencies can be easily evaluated and compensated even when they are affected by dev iations of element values and parasitic elements. The compensation req uires detection of both frequency and excess phase shifts of the integ rators. Their two values are electrically detected by two detection sy stems usually used in the conventional frequency tuning system, The pr oposed system is stable, simple and easy to be implemented on an integ rated circuit. As an example a 4th-order biquad bandpass filter with 1 0 MHz center frequency, 2 MHz passband width, and 0.5 dB passband ripp les is designed using a bipolar process. Simulation results by SPICE s how the effectiveness of the proposed system.