Analog integrated filter circuit
AssigneeMotorola, Inc.
InventorsBarry L. Jason, Scott M. Hall, Richard L. Valley
Life of this patent
Estimating the term…
Abstract
An analog integrated filter circuit includes a capacitance multiplier combined with a DC bias controlled current circuit designed to render the filter circuit insensitive to changes in the parameter values of the components caused by process variations or a temperature change therein. The capacitance multiplier circuit includes grounded or ungrounded capacitance multipliers in different combinations operatively coupled to the DC bias controlled current circuit so that the capacitance multiplier circuit can be used to construct a predictable low pass, bandpass or high pass filter circuit with frequency characteristics that do not vary over temperature.
Claims10
An analog integrated filter comprising:
- capacitance multiplier means, including a capacitor (C), having a first and a second terminal, for providing an effective capacitance M.sub.f times that of the capacitor, and including a feedback impedance dependent upon an applied current;
- resistance means, coupled to the capacitance multiplier means, for providing resistance operative in conjunction with the effective capacitance to provide filtering;
- and, DC bias-controlled current supplying circuit, coupled to the capacitance multiplier means, for providing a DC bias-controlled current having a temperature dependence which substantially cancels the cumulative temperature dependence of the feedback impedance and the resistance means, so that the filter has a constant operating frequency response characteristic as the filter operates over a range of temperatures.
Dependencies are inferred from the claim text.