Patent ID: 7061310

Claim:
An all-pass filter circuit comprising: a first terminal to which an input signal is input; a second terminal from which an output signal is output; a capacitor having a first electrode connected to the input terminal and a second electrode; a current amplifier circuit having a first input terminal to which a first signal output from the capacitor is input, a first output terminal and a control terminal to which a control signal for controlling conductance of the current amplifier circuit, the current amplifier circuit generating a second signal based on the conductance, the second signal being output from the first output terminal; and an adder circuit having a second input terminal to which the input signal is input and a second output terminal, and adding the second signal and the input signal together to output the output signal from the second output terminal, the adder circuit including a first MOS transistor having a first drain, a first gate and a first source, the first gate being connected to the first terminal, and a second MOS transistor having a second drain to which the input signal is input, a second gate and a second source, the second drain and the second gate being connected together, the second source being connected to the first source, and the second gate outputting the output signal.