| 摘要 |
PURPOSE:To obtain a circuit obtaining a high Q by providing a 3rd amplifier applying voltage amplification in opposite polarity to a difference voltage as an input signal inputted to a couple of bipolar differential input terminals of a 1st amplifier circuit in comparison with said 1st amplifier circuit and supplying it to the other terminal of a 1st capacitor. CONSTITUTION:An input voltage Vin inputted from an input terminal 1 is multiplied with a coefficient (b) by a coefficient circuit 2 and outputted as a level of b.Vin. An amplifier circuit 5 converts a voltage difference between the output of the coefficient circuit 2 and an output voltage Vout into a current and outputs it, it is integrated by a capacitor C1 and extracted as a voltage, and a signal being the result of amplifying a difference voltage between the output voltage Vout and the output signal of the coefficient circuit 2 is fed from an amplifier circuit 4 via the capacitor C1 and a signal voltage V' is obtained. The Q of the filter circuit is increased by a multiple of 1/(1-M) (M is the gain of the amplifier circuit 4) with respect to the capacitance of the capacitors C1, C2 and mutual conductances gm1, gm2 of amplifier circuits 5, 6.
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