| 摘要 |
A trans-conductance filter circuit (50) with an expanded cut-off frequency range is provided. The cut-off frequency of a trans-conductance filter circuit is changed by varying the current mirror ratio of a current mirror circuit. This mirror ratio is varied by changing the output current of a constant current source, or by switching among the respective action states of multiple transistors (P3, P4, P5, P6) the actions of which are invoked within constant current regions. The variable cut-off frequency range can be expanded without losing the constant current attributes of the transistors. <IMAGE>
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