Patent ID: 6812780
Filing Date: 2004-11-02
Classification: H03D,H03H

Abstract:
A filter circuit comprising:an input terminal which is input with a first current, and which is coupled with a first node; a capacitor, of which one terminal is coupled with the first node, of which the other terminal is coupled with a second node, and which integrates the first current and outputs a voltage; a transconductance means, of which one terminal is coupled with the first node, of which another terminal is coupled with the second node, of which the other terminal is coupled with a third node, and which outputs a second current being proportional to the voltage to the third node, wherein the transconductance means comprises a first current source which is supplied with a supply voltage and which is coupled with the first node, a second current source which is supplied with the supply voltage and which is coupled with the third node, a third current source which is coupled with the second node; a first transistor which has a control electrode coupled with the third node, a first electrode coupled with the first current source and a second electrode coupled with the third current source, and a second transistor which has a control electrode coupled with a voltage supply circuit, a first electrode coupled with the second current source and a second electrode coupled with the third current source, the voltage supply circuit supplying a control voltage for the control electrode of the second transistor and being coupled with the second node, an output terminal which is coupled with the first node, and which outputs the voltage.