Patent ID: 7764116
Filing Date: 2010-07-27
Classification: H03H

Abstract:
1. A cutoff frequency adjusting method for adjusting a cutoff frequency of a GmC filter circuit which has a capacitor and an Operational Transconductance Amplifier (OTA) circuit with a controllable Gm value and a first switch provided between an output terminal of the OTA circuit and an electrode of the capacitor, comprising: detecting a Gm value of the OTA circuit based on a voltage of the capacitor which is charged by an output of the OTA circuit; generating a control signal to the OTA circuit using a control circuit comprising a code generating circuit coupled to an adjustable current source in response to the detected Gm value; setting a cutoff frequency of the GmC circuit to a certain value by controlling the Gm value of the OTA circuit constant based on the control signal; and, wherein the capacitor is charged for a period when the first switch is in an ON state.