Active filter
First Claim
Patent Images
1. An active filter comprising:
- a current differential amplifier having an inverting input terminal, a non-inverting input terminal and an output terminal and supplied with an input signal at the non-inverting input terminal;
a capacitor connected between the output terminal of said current differential amplifier and a power source, for storing charges according to an output signal of said current differential amplifier; and
an adding circuit for adding the input signal and the output signal of said current differential amplifier, the input signal and the output signal being divided by means of resistors, and an output signal of said adding circuit being supplied to an output terminal and to the inverting input terminal of said current differential amplifier.
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Abstract
An input signal is supplied to the non-inverting input terminal of a current differential amplifier. A capacitor is connected between the output terminal of the current differential amplifier and a power source and the capacitor stores charges according to an output signal of the current differential amplifier. The input signal and an output signal of the current differential amplifier are supplied to resistors via buffer circuits and signals divided by the resistors are added together by a buffer circuit and output from an output terminal and at the same time fed back to the inverting input terminal of the current differential amplifier.
109 Citations
16 Claims
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1. An active filter comprising:
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a current differential amplifier having an inverting input terminal, a non-inverting input terminal and an output terminal and supplied with an input signal at the non-inverting input terminal; a capacitor connected between the output terminal of said current differential amplifier and a power source, for storing charges according to an output signal of said current differential amplifier; and an adding circuit for adding the input signal and the output signal of said current differential amplifier, the input signal and the output signal being divided by means of resistors, and an output signal of said adding circuit being supplied to an output terminal and to the inverting input terminal of said current differential amplifier. - View Dependent Claims (2, 3)
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4. An active filter comprising:
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a filter input terminal supplied with an input signal; a current differential amplifier having an inverting input terminal, a non-inverting input terminal and an output terminal and the non-inverting input terminal being connected to said filter input terminal; a capacitor connected between the output terminal of said current differential amplifier and a first power source potential, for storing changes according to an output signal of said current differential amplifier; a first buffer circuit having an input terminal connected to said filter input terminal; a first resistor connected at one end to an output terminal of said first buffer circuit; a second buffer circuit having an input terminal connected to the output terminal of said current differential amplifier; a second resistor connected at one end to an output terminal of said second buffer circuit; a third buffer circuit having an input terminal connected to the other ends of said first and second resistors and an output terminal connected to the inverting input terminal of said current differential amplifier; and a filter output terminal connected to the output terminal of said third buffer circuit. - View Dependent Claims (5, 6, 7, 8, 9)
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10. An active filter comprising:
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a filter input terminal for receiving an input signal; a current differential amplifier having inverting input terminal, a non-inverting input terminal coupled to said filter input terminal, and an output terminal for outputting a differential amplifier output signal; and an adding circuit for adding the input signal and the differential amplifier output signal, said adding circuit having input terminals for receiving the input signal and the differential amplifier output signal and an output terminal for outputting an adding circuit output signal, the inverting input of said current differential amplifier coupled to the output terminal of said adding circuit; and a filter output terminal coupled to the output terminal of said adding circuit. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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Specification