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US 6,271,720 B1Granted
Operational filter building block
AssigneeLinear Technology Corporation
InventorNello George Sevastopoulos
Life of this patent
Estimating the term…
Abstract
A 3-terminal operational filter circuit is presented that can be used to construct various types of active filters. The filter circuit can be used to construct various orders of low pass, band-pass, high pass, and notch filters by simply coupling a few circuit elements (e.g., resistors and capacitors) to the filter circuit terminals. By cascading filter circuits, various types of higher order filters can constructed. The filter circuit can be manufactured with particular internal resistance and capacitance to enable the circuit to operate within a selected range of center frequencies. Users can then select a particular center frequency, notch frequency, quality factor, and gain of the filter circuit by selecting particular values for the circuit elements coupled to the filter circuit terminals.
Claims26
An electrical filter circuit operative to provide a notch frequency response comprising:
- an operational filter circuit having an input terminal, a first output terminal for providing a first frequency response, a second output terminal for providing a second frequency response, and an operational amplifier having an input coupled to said input terminal and an output coupled to said first output terminal and to said second output terminal;
- a first resistor coupled between said first output terminal and said input terminal;
- a second resistor coupled between said input terminal and said second output terminal;
- a third resistor coupled between an input signal source and said input terminal;
- a summing circuit having a summing circuit input terminal, a summing circuit output terminal, and an operational amplifier having an input coupled to said summing circuit input terminal and an output coupled to said summing circuit output terminal;
- a capacitor coupled between said second output terminal and said summing circuit input terminal;
- and
- a fourth resistor coupled between said first output terminal and said summing circuit input terminal;
- wherein:
- said summing circuit output terminal provides a notch frequency response.
7 more elements
An electrical filter circuit operative to provide a notch frequency response comprising:
- an operational filter circuit having an input terminal, a first output terminal for providing a first frequency response, a second output terminal for providing a second frequency response, and an operational amplifier having an input coupled to said input terminal and an output coupled to said first output terminal and to said second output terminal;
- a first resistor coupled between said first output terminal and said input terminal;
- a second resistor coupled between said input terminal and said second output terminal;
- a third resistor coupled between an input signal source and said input terminal;
- a capacitor coupled between said input signal source and said input terminal;
- a summing circuit having a summing circuit input terminal, a summing circuit output terminal, and an operational amplifier having an input coupled to said summing circuit input terminal and an output coupled to said summing circuit output terminal;
- a fourth resistor coupled between said second output terminal and said summing circuit input terminal;
- and
- a fifth resistor coupled between said input signal source and said summing circuit input terminal;
- wherein:
- said electrical filter circuit has a center frequency, and
- said summing circuit output terminal provides a notch frequency response having a notch at a frequency greater than said center frequency.
9 more elements
An electrical filter circuit operative to provide a notch frequency response comprising:
- an operational filter circuit having an input terminal, a first output terminal for providing a first frequency response, a second output terminal for providing a second frequency response, and an operational amplifier having an input coupled to said input terminal and an output coupled to said first output terminal and to said second output terminal;
- a first resistor coupled between said first output terminal and said input terminal;
- a second resistor coupled between said input terminal and said second output terminal;
- a third resistor coupled between an input signal source and said input terminal;
- a capacitor coupled between said input signal source and said input terminal;
- a summing circuit having a summing circuit input terminal, a summing circuit output terminal, and an operational amplifier having an input coupled to said summing circuit input terminal and an output coupled to said summing circuit output terminal;
- a fourth resistor coupled between said first output terminal and said summing circuit input terminal;
- and
- a fifth resistor coupled between said input signal source and said summing circuit input terminal;
- wherein:
- said electrical filter circuit has a center frequency, and
- said summing circuit output terminal provides a notch frequency response having a notch at a frequency less than said center frequency.
9 more elements
A method of constructing an electrical filter operative to provide a notch frequency response, said method comprising:
- providing an operational filter circuit having an input terminal for receiving an input signal from an input signal source, a first output terminal for providing a low Pass frequency response, and a second output terminal for providing a band-pass frequency response;
- providing a summing circuit having a summing circuit input terminal and a summing circuit output terminal;
- coupling a capacitor in series between said second output terminal and said summing circuit input terminal;
- and
- coupling a resistor in series between said first output terminal and said summing circuit input terminal;
- wherein:
- said summing circuit output terminal provides a notch frequency response.
4 more elements
A method of constructing an electrical filter operative to provide a notch frequency response, said method comprising:
- providing an operational filter circuit having an input terminal for receiving an input signal from an input signal source, a first output terminal for providing a low pass frequency response, and a second output terminal for providing a band-pass frequency response;
- providing a summing circuit having a summing circuit input terminal and a summing circuit output terminal;
- coupling a resistor in series between said second output terminal and said summing circuit input terminal;
- and
- coupling a second resistor in series between said input signal source and said summing circuit input terminal;
- wherein:
- said electrical filter has a center frequency, and said summing circuit output terminal provides a notch frequency response having a notch at a frequency greater than said center frequency.
4 more elements
A method of constructing an electrical filter operative to provide a notch frequency response, said method comprising:
- providing an operational filter circuit having an input terminal for receiving an input signal from an input signal source, a first output terminal for providing a low Pass frequency response, and a second output terminal for providing a band-pass frequency response;
- providing a summing circuit having a summing circuit input terminal and a summing circuit output terminal;
- coupling a resistor in series between said first output terminal and said summing circuit input terminal;
- and
- coupling a second resistor in series between said input signal source and said summing circuit input terminal;
- wherein:
- said electrical filter has a center frequency, and
- said summing circuit output terminal provides a notch frequency response having a notch at a frequency less than said center frequency.
5 more elements
A method of creating a notch frequency response, said method comprising:
- filtering an input signal to obtain a band-pass frequency response;
- filtering said input signal to obtain a low pass frequency response;
- coupling said band-pass frequency response through a capacitor to a summing node;
- coupling said low pass frequency response through a resistor to said summing node;
- and
- summing said responses at said summing node to create said notch frequency response.
3 more elements
A method of creating a notch frequency response, said method comprising:
- phase shifting an input signal;
- filtering said phase-shifted input signal to obtain a band-pass frequency response;
- coupling said band-pass frequency response through a first resistor to a summing node;
- coupling said input signal through a second resistor to said summing node;
- and
- summing said band-pass frequency response and said input signal at said summing node to create said notch frequency response.
3 more elements
A method of creating a notch frequency response, said method comprising:
- phase shifting an input signal;
- filtering said phase-shifted input signal to obtain a low pass frequency response;
- coupling said low pass frequency response through a first resistor to a summing node;
- coupling said input signal through a second resistor to said summing node;
- and
- summing said low pass frequency response and said input signal at said summing node to create said notch frequency response.
3 more elements
Dependencies are inferred from the claim text.