Patent ID: 6516069
Filing Date: 2003-02-04
Classification: H04R

Abstract:
A microphone filter comprising:a capacitor having a first end, and a second end into which an output from a microphone is fed; a first transistor having a first current electrode connected to said first end of said capacitor, a second current electrode to which a first fixed potentials applied, and a control electrode, a second transistor having a first current electrode, a second current electrode which is connected to said second current electrode of said first transistor, and a control electrode which is connected to said control electrode of said first transistor; and a constant current source connected to said first current electrode and said control electrode of said second transistor such that a constant current of a same value as an output current from the constant current source flows both between the first and second current electrodes of the second transistor and between the first and second current electrodes of the first transistor thereby forming a current mirror circuit.