Second Order Switched-Capacitor Filter with Single-Element Tuning of the Pole Frequency

Three schemes of second-order low-pass filters on switched-capacitors are analyzed. The investigated filters differ in the ideology of their construction, but at the same time they have one property uniting them - the possibility of tuning the pole frequency. The specified property is provided by changing the parameter of only one element - resistance of a resistor or capacitance of one capacitor, which is a significant advantage in comparison with other schemes of filters of this class. The novelty of such circuit solutions has been confirmed by patents. It is shown that in the considered schemes the sensitivity of the realized quality factor to the tuning element is equaled to zero, by what the possibility of one-element tuning of the pole frequency is achieved. An important distinguishing feature of the considered schemes of SC-filters of lower frequencies from traditional ones is that they contain a smaller number of passive elements for realization of the transfer function of the second order.