| 摘要 |
By a gain control circuit which has: a first differential input circuit comprising a differential pair of transistors Tr1 and Tr3 in which transistors Tr2 and Tr4 connected to diodes are inserted; a second differential input circuit comprising a pair of the transistor Tr3 and a transistor Tr5; and a current source circuit comprising a transistor Tr6 and an emitter resistor R3, and to which first to third individual control input signals VCLS1 to VCLS3 each having a predetermined inclination and an offset value, obtained by shifting the level of a control input signal VCNT are supplied, gain control signals VAGC having a linear characteristic, a monotone increase characteristic of which curve opens upwards, and a monotone increase characteristic of which curve opens sharply upwards are supplied in accordance with a monotone increase region of which curve opens upwards, a linear region, and a monotone increase region of which curve opens downwards, respectively, of a differential pair of transistors Tr11 and Tr12 and a differential pair of transistors Tr13 and Tr14 at the second stage of a differential amplification circuit.
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