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US 3,946,328 AGranted
Functionally tunable active filter
AssigneeNorthern Electric Company Limited
InventorStalin A. Boctor
Life of this patent
Estimating the term…
Abstract
A family of RC active filters in which band-pass, low-pass notch, high-pass notch, band-stop and all-pass second order sections may be realized. The filters provide unidirectional functional tuning of the four basic parameters .omega..sub.o, Q.sub.o, .omega..sub.z and Q.sub.z through resistive trimming.
Claims10
An RC functionally tunable active filter comprising:
- input, output and common terminals;
- a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal;
- a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier;
- a second capacitor connected between the inverting input and the output of the differential amplifier;
- a second resistor connected between the junction of the first capacitor and resistor, and the common terminal;
- a third resistor connected between said junction and the output of the differential amplifier;
- and
- conductive means connected between the noninverting input of the differential amplifier and the common terminal;
- the differential amplifier, resistors, capacitors and conductive means coacting such that variations in resistance of the first and/or third resistors affect the pole resonant frequency .omega..sub.o, and variations in resistance of the second resistor affect the pole quality factor Q.sub.o but not .omega..sub.o, thereby enabling a unidirectional sequence of functional tuning of the filter.
6 more elements
An RC functionally tunable active filter comprising:
- input, output and common terminals;
- a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter;
- a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier;
- a second capacitor connected between the inverting input and the output of the differential amplifier;
- a second resistor connected between the junction of the first capacitor and resistor, and the common terminal;
- a third resistor connected between said junction and the output of the differential amplifier;
- and
- the noninverting input of the differential amplifier being connected to the common terminal;
- the differential amplifier, resistors and capacitors coacting such that variations of the resistance of the first and/or third resistors affect the pole resonant frequency .omega..sub.o, and variations in resistance of the second resistor affect the pole quality factor Q.sub.o but not .omega..sub.o ;
- and
- the values of the resistors and capacitors are such that:
- .omega..sub.z = 0, whereby the filter functions as a band-pass filter.
9 more elements
An RC functionally tunable active filter comprising:
- input, output and common terminals;
- a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter;
- a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier;
- a second capacitor connected between the inverting input and the output of the dfferential amplifier;
- a second resistor connected between the junction of the first capacitor and resistor, and the common terminal;
- a third resistor connected between said junction and the output of the differential amplifier;
- a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal;
- a fifth resistor connected between the input terminal and the noninverting input of the differential amplifier;
- and
- a sixth resistor connected between the inverting input of the differential amplifier and the common terminal;
- the differential amplifier, resistors and capacitors coacting such that variations in the resistance of the first and/or third resistors affect the pole resonant frequency .omega..sub.o, variations in resistance of the second resistor affect the pole quality factor Q.sub.o but not .omega..sub.o, variations in resistance of the sixth resistor affect the zero resonant frequency .omega..sub.z but not .omega..sub.o and Q.sub.o, and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q.sub.z but not .omega..sub.o, .omega..sub.z and Q.sub.o ;
- and
- the values of the resistors and capacitors are such that:
- .omega..sub.z >
- .omega..sub.o , and Q.sub.z = .infin., whereby the filter functions as a low-pass notch filter.
12 more elements
An RC functionally tunable active filter comprising:
- input, output and common terminals;
- a differential amplifier having inverting and noninverting inputs, and an output connected to the output terminal of the filter;
- a first capacitor and a first resistor serially connected between the input terminal and the inverting input of the differential amplifier;
- a second capacitor connected between the inverting input and the output of the differential amplifier;
- a second resistor connected between the junction of the first capacitor and resistor, and the common terminal;
- a third resistor connected between said junction and the output of the differential amplifier;
- a fourth resistor connected between the noninverting input of the differential amplifier and the common terminal;
- a fifth resistor connected between the input terminal and the noninverting input of the differential amplifier;
- and
- a sixth resistor and a third capacitor connected in shunt between the inverting input of the differential amplifier and the common terminal;
- the differential amplifier, resistors and capacitors coacting such that variations in the resistance of the first and/or third resistors affect the pole resonant frequency .omega..sub.o, variations in resistance of the second resistor affect the pole quality factor Q.sub.o but not .omega..sub.o, variations in resistance of the sixth resistor affect the zero resonant frequency .omega..sub.z but not .omega..sub.o and Q.sub.o, and variations in resistance of the fourth and/or fifth resistors affect the zero quality factor Q.sub.z but not .omega..sub.o, .omega..sub.z and Q.sub.o.
8 more elements
Dependencies are inferred from the claim text.