Patent ID: 6369645
Filing Date: 2002-04-09
Classification: H03H

Abstract:
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.