1000:1 Tuning Voltage-Controlled Filter

A standard dual integrator filter can be constructed using a few CA3080s. By varying LABC, the reso
1000:1 Tuning Voltage-Controlled Filter - schematic

nant frequency can be swept over a 1000:1 range. At IC1, three are current-controlled integrators. At IC2, four are voltage followers that serve to buffer the high-impedance outputs of the integrators. A third CA3080 (IC5) is used to control the Q factor of the filter. The resonant frequency of the filter is linearly proportional to /abc· Hence, this unit is very useful in producing electronic music. Two outputs are produced: a low-pass and a bandpass response.

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