Study of Discrete Analog Filters with Pole Frequency Adjustment Using General Feedback Resistors

Three new modifications of second-order low-frequency discrete analog filters (DAFs) based on switched capacitors have been developed and studied. A distinctive feature of the DAFs under consideration is the presence of two resistors in the general feedback circuit. This allows, at constant values of the capacitances of the frequency-setting capacitors and a fixed switching frequency of electronic switches, to control the frequency of the DAF pole by changing the resistance ratio of these resistors. The basic equations for the low-pass filter gain at zero frequency, the low-pass filter gain at the pole frequency, as well as formulas for calculating the pole frequency and pole attenuation are given. In the Micro-Cap environment, computer simulation of the proposed modifications of the DAF was performed, which shows that the considered circuit solutions perform the functions of a low-pass filter.