| 摘要 |
PURPOSE:To obtain a filter circuit with a wide dynamic range, high band, high S/N and low energy consumption especially suitable for a low-pass filter without enlarging a chip size. CONSTITUTION:The low-pass filter 10 is a mutually variable conductance type differential amplifier circuit and composed of the two steps of operational amplifiers 11 and 12 and buffer 13. Parasitic capacitor Crm and C1P parasitic on a PNP load transistor and an NPN transistor for differential input are defined as ground capacitors, and connection midpoints P10 and P11 of the load transistor and the transistor for differential input connecting these ground capacitors are activated at the intermediate potential of a power supply voltage and a ground potential. Therefore, the voltage depending characteristic of the ground capacitor can be fixed by canceling the voltage depending characteristic of the parasitic capacitor.
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