FILTER CIRCUIT

摘要

The invention relates to a filter circuit adapted for integrated circuitry design and constituted by transistors or field effect transistors for controlling a frequency band, for example, in an amplification circuit of a signal receiving section in an optical communication system. The filter circuit comprises a first transistor (T1), of which a base or gate is grounded through a first resistance (R1) in a high frequency-like manner, a second resistance (R2) and a capacitor (C1) each having one end thereof connected to an emitter or source of the first transistor (T1) and the other end thereof grounded in a high frequency-like manner. The filter circuit is constitued by a circuit which receives an electric current (Iin) at connecting points of the second resistance (R2), the capacitor (C1) and the first transistor (T1) and outputs a collector or drain current (Iout) of the first transistor.