| 摘要 |
PROBLEM TO BE SOLVED: To provide an amplifier circuit with a small resistance and a small capacitance, which has a small area and can reduce an offset. SOLUTION: A differential amplifier circuit consists of transistors(TRs) M2, M1 whose gate electrodes are used for positive and negative input terminals, resistive elements RN1, RP1, and a constant current source I1. An amplifier having bipolar inputs and outputs amplifies outputs of the differential amplifier circuit to provide the amplified outputs to positive and negative output terminals. An amplifier circuit consisting of a resistor RP3, TRs M3, M4 and a constant current source I2 and a capacitor CP having an equivalent capacitance multiplied by a multiple of a gain eliminates an AC component of signals from the positive and negative output terminals and an amplifier circuit consisting of a resistor RN3, TRs M8, M7 and a constant current source I4 and a capacitor CN having an equivalent capacitance multiplied by a multiple of a gain eliminates the AC component of the signals from the positive and negative output terminals. The signals whose AC component is eliminated are negatively fed back to the inputs of the amplifier with a differential amplifier circuit consisting of TRs M5, M6 and a constant current source I3. The negative feedback can reduce the offset of the amplifier. Since each equivalent capacitor is multiplied by a gain with the mirror effect, a smaller resistance and a smaller capacitance are enough to realize the same time constant.
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