| 摘要 |
PURPOSE:To obtain an amplifier circuit device capable of automatic gain control with high precision by cascading signal amplifier circuits formed by connecting plural amplifiers in parallel and controlling output gains of respective stages with a digital signal which follows up variation in input level. CONSTITUTION:This amplifier circuit device is constituted including a multistage amplifier circuit 10 composed of three signal amplifier circuits which connect with an input signal V1 and amplifier it, a detector 1 which detects part of their output, a comparison circuit 2 which codes the level difference between a detector output V2 and a reference voltage V0 into a binarization signal, an up/down counter 3 which outputs up the binarization output V3 with a clock signal CK, a ROM signal conversion device 4 which is addressed with a digital counted value V4 outputted by the counter 3 and output signals V5-V7 for connecting respective stages of amplifiers (A1-A12) of the multistage amplifier circuit 10 selectively. The clock signal CK of the counter 3 is speeded up and the number of cascaded stages of the signal amplifier circuit and the number of parallel differential amplifiers are increased to obtain an amplifier circuit which performs free gain control with high precision while following up wide- range level variation of the input signal V1.
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