Condenser microphone and its impedance converter

Abstract

An condenser microphone is provided herein having an impedance converter directly coupled to the transducer of the condenser microphone. The impedance converter includes an active element for impedance conversion and a control circuit for filtering an AF output signal outputted from the active element in order to retrieve a bias direct voltage as a set value, the bias direct voltage being supplied to the other terminal of the bias resistor. A coupling capacitor between the condenser transducer and the active element is eliminated so that a bias resistor acting as a source of noise can be eliminated as well and the remaining bias resistor can be increased.

Description

technical field [0001] The present invention relates to condenser microphones using DC-coupled impedance conversion. Background technique [0002] For externally polarized condenser microphones, the change in transducer capacitance is related to the acoustic sound pressure on the transducer diaphragm (such as a singer's singing voice). In order to convert the change in capacitance into an electrical signal, the transducer is charged with a constant DC voltage to make it electrostatically charged. [0003] For a transducer with stable and constant static electricity, the relationship between its capacitance and capacitor voltage is: [0004] Uc=Qc / C [0005] Among them, Uc represents the DC voltage applied to the capacitor, Qc represents the electrostatic charge on the capacitor, and C represents the capacitance of the capacitor. [0006] The above relationship is only valid under the condition that the electrostatic charge Qc on the transducer remains constant. Therefore...

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Problems solved by technology

[0015] (2) The leakage current of the JFET gate will flow through the large resistance bias resistor R2

[0016] (3) The leakage current caused by the pollution of the printed circuit board will also flow through the resistor R2, so the upper limit of the resistance value of the resistor will be further limited

[0020] Signal loss due to capacitive voltage divider

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