Property of Butterworth Type Low-Pass Filter Used in Lock-in Amplifier for Precise Capacitance Transducer
Based on the fact that Op Amps of Butterworth low-pass filter is non-ideal, the transfer function of VCVS type two-order Butterworth LPF based on non-ideal Amps is deduced theoretically. The influence of non-ideal characteristic on filter is studied, and the relationship between step response and control time of filter based on non-ideal Amps and periphery circuit parameters is analyzed and calculated. The effect of LPF with non-ideal Amps on real-time of tiltmeter is evaluated. The control time and cutoff frequency of LPF are tested by experiment and the results are basically in accord with the theoretical ones.
KeywordsControl Time Step Response Output Impedance Circuit Parameter Ideal Filter
This work was supported by the National Nature Science Foundation of China under Grant Nos. 61004130 and the Fundamental Research Funds for the Central Universities under Grant Nos. HUECFL20111107.
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