Low-pass filter with a summing function
First Claim
1. A low-pass filter comprising:
- first through N-th positive filter input terminals supplied with first through N-th positive filter input signals, respectively, where N represents a first positive integer which is not less than two;
first through M-th negative filter input terminals supplied with first through M-th negative filter input signals, respectively, where M represents a second positive integer which is not less than two;
an operational amplifier having inverting and noninverting input ports, and inverting and noninverting amplifier output ports for producing inverted and noninverted amplifier output signals, respectively;
a first amplifier input resistor having an end connected to the noninverting input port of said operational amplifier and another end connected to a positive common node;
a second amplifier input resistor having an end connected to the inverting input port of said operational amplifier and another end connected to a negative common node;
an amplifier input capacitor connected between the positive and the negative common nodes;
a first filter feedback resistor connected between the positive common node and the inverting amplifier output port of said operational amplifier;
a second filter feedback resistor connected between the negative common node and the noninverting amplifier output port of said operational amplifier;
a first filter feedback capacitor connected between the noninverting input port of said operational amplifier and the inverting amplifier output port of said operational amplifier;
a second filter feedback capacitor connected between the inverting input port of said operational amplifier and the noninverting amplifier output port of said operational amplifier;
first through N-th positive input impedance circuits connected between the positive common node and said first through said N-th positive filter input terminals, respectively;
first through M-th negative input impedance circuits connected between the negative common node and said first through said M-th negative filter input terminals, respectively;
an inverting filter output terminal, connected to the inverting amplifier output port of said operational amplifier, for producing the inverted amplifier output signal as an inverted filter output signal; and
a noninverting filter output terminal, connected to the noninverting amplifier output port of said operational amplifier, for producing the noninverted amplifier output signal as a noninverted filter output signal.
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Accused Products
Abstract
In a low-pass filter (10) having a filter input terminal (10-i1) supplied with a filter input signal (V1) and comprising an operational amplifier (11) and other peripheral passive elements (Rin, Cin, Rf, Cf, R1-1), the low-pass filter (10) further has an additional filter input terminal (10-i2) supplied with an additional filter input signal (V2) and comprises an additional filter input resistor (R1-2) connected between the additional filter input terminal (10-i2) and a common node (a0). The operational amplifier (11) has an inverting input port (11-1), a noninverting input port (11-2) connected to the reference voltage terminal (12), and an amplifier output port (11-3) for producing an amplifier output signal. Connected to the amplifier output port (11-3) of the operational amplifier (11), a filter output terminal (10-o) produces the amplifier output signal as a filter output signal. Thereby, the low-pass filter (10) sums up the filter input signals (V1, V2) to obtain a summed signal and removes a high frequency component from the summed signal to make the filter output terminal (10-o) produce a low-pass filtered signal as the filter output signal.
23 Citations
2 Claims
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1. A low-pass filter comprising:
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first through N-th positive filter input terminals supplied with first through N-th positive filter input signals, respectively, where N represents a first positive integer which is not less than two;
first through M-th negative filter input terminals supplied with first through M-th negative filter input signals, respectively, where M represents a second positive integer which is not less than two;
an operational amplifier having inverting and noninverting input ports, and inverting and noninverting amplifier output ports for producing inverted and noninverted amplifier output signals, respectively;
a first amplifier input resistor having an end connected to the noninverting input port of said operational amplifier and another end connected to a positive common node;
a second amplifier input resistor having an end connected to the inverting input port of said operational amplifier and another end connected to a negative common node;
an amplifier input capacitor connected between the positive and the negative common nodes;
a first filter feedback resistor connected between the positive common node and the inverting amplifier output port of said operational amplifier;
a second filter feedback resistor connected between the negative common node and the noninverting amplifier output port of said operational amplifier;
a first filter feedback capacitor connected between the noninverting input port of said operational amplifier and the inverting amplifier output port of said operational amplifier;
a second filter feedback capacitor connected between the inverting input port of said operational amplifier and the noninverting amplifier output port of said operational amplifier;
first through N-th positive input impedance circuits connected between the positive common node and said first through said N-th positive filter input terminals, respectively;
first through M-th negative input impedance circuits connected between the negative common node and said first through said M-th negative filter input terminals, respectively;
an inverting filter output terminal, connected to the inverting amplifier output port of said operational amplifier, for producing the inverted amplifier output signal as an inverted filter output signal; and
a noninverting filter output terminal, connected to the noninverting amplifier output port of said operational amplifier, for producing the noninverted amplifier output signal as a noninverted filter output signal. - View Dependent Claims (2)
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Specification