MOSFET-C FILTER WITH LOW EXCESS NOISE AND ACCURATE AUTOMATIC TUNING

Continuous-time integrated filters having a maximum dynamic range at the audio-frequency range are obtained using MOSFET-C filters. In combination with a careful design of the applied symmetrical amplifiers in a BiCMOS technology, the detrimental influence of 1/f noise can be minimized. A 98-dB dynamic range (THD < 0.3%) is obtained in a realized fifth-order Butterworth low-pass filter, while the overall 1/f noise corner frequency is limited to 250 Hz. Automatic adjustment of the filter cutoff frequency is performed using a novel all-silicon automatic tuning system that, compared with traditional automatic tuning system, demands reduced overhead circuitry.