High-pass filter circuit and band-pass filter circuit

A high-pass filter circuit comprising:

• a capacitor configured to input an input signal;
• a signal output circuit including an operational amplifier having a non-inverting input connected to an output terminal of the capacitor, to buffer-amplify the input signal to output a high pass filtered signal;
• and
• a resistor connected (i) between the output terminal of the capacitor and a prescribed non-zero bias voltage and (ii) between the non-inverting input of the operational amplifier and the prescribed bias voltage,
• wherein the resistor is formed on an SOI semiconductor substrate and includes two PN junction diodes that are inversely connected to each other in parallel, the two PN junction diodes have an approximately zero potential difference between an anode and cathode of the PN junction diodes, and the two PN junction diodes set a bias point of the non-inverting input of the operational amplifier to the prescribed non-zero bias voltage to provide the high pass filtered signal with a very low cutoff frequency.