| 摘要 |
PROBLEM TO BE SOLVED: To attain low power consumption by distributing constant current between the emitter and collector of a first and a second transistors. SOLUTION: When an input signal Vin with a certain frequency is inputted to a signal input terminal l4, the input signal Vin is impressed to the emitter side of a transistor P4, a potential difference is proportion to Vt is generated between the emitter and the base of the transistor P4, and current I is allowed to flow between the emitter and base. The current I is allowed to flow from an output terminal 5 to a resistor R so that an output signal Vout outputted from a signal output terminal 7 is only a signal with a frequency less than 1/2πC((Vt+I)+R). As a result, only the output signal Vout with a frequency less than a cut-off frequency depending on the output impedance of the transistor P4 is outputted. Thus, an operating amplifier 2 constituted of only four transistors P3-P6 is used so that current to be consumed by the operating amplifier 2 is reduced.
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