Second-Order Discrete-Analog Filters on Switched Capacitors with Two Electronic Keys

Two new modifications of second-order low-frequency discrete-analog filters (DAFs) based on switched capacitors with two electronic keys have been developed and investigated. The first modification contains a resistive signal adder based on a buffer amplifier, in the second modification the signal adder is implemented on a differential difference operational amplifier. The basic formulas for the transmission coefficient at zero frequency and pole frequency, and also a frequency and attenuation of the pole are given. The transmission coefficient of new circuits in the passband does not depend on the capacitances of the frequency-setting capacitors. Computer modeling was performed in the Micro-Cap environment, which confirms the coincidence of the calculated main parameters of the DAF and their time characteristics. The developed DAFs were studied at various input signal frequencies, which differ by several orders of magnitude, including the low, medium and high frequency ranges. It is shown that the graph of the DAF output signal has a “step” character, which corresponds to the physical processes of signal conversion in filters of the class under consideration. The low parametric sensitivity of presented DAF circuits is achieved by the fact that the pole attenuation and transmission coefficient of such DAFs cease to depend on the parameters of the tuning elements.