| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic offset erasure circuit for which an external capacitor is not required.SOLUTION: An automatic offset erasure circuit includes: a low-pass filter 2 for low-pass-filtering a main signal; an amplifier 1 for boosting a DC potential of an output signal from the low-pass filter 2; and a low-pass filter 3 for low-pass-filtering an output signal of the amplifier 1 and negatively feeding the output signal back to an amplifier of a main signal system. The low-pass filter 3 is comprised of: resistors rd1, rd2, the one terminal of which is connected to an output terminal of the amplifier 1; capacitors cd3, cd4 inserted between output-side terminals of the resistors rd1, rd2 and a ground thereof; and a mirror multiplication capacitor connected to the output-side terminals of the resistors rd1, rd2. The mirror multiplication capacitor is comprised of: a capacitance multiplication amplifier the input terminal of which is connected to the output-side terminals of the resistors rd1, rd2; and capacitors cd1, cd2 provided between the input terminal and an output terminal of the capacitance multiplication amplifier. |
