Microphone amplifier

A technology of amplifiers and operational amplifiers, applied in the direction of amplifiers, low-frequency amplifiers, improved amplifiers to reduce the harmful effects of internal resistance, etc., can solve the problems of increased noise floor, etc., to achieve reduced parasitic capacitance, good S/N, and noise floor produces a smaller effect

CN101115328AInactive Publication Date: 2008-01-30SANYO ELECTRIC CO LTD +1
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Patent Information

Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Publication Date
2008-01-30
Estimated Expiration
Not applicable · inactive patent

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Abstract

With a microphone amplifier using an operational amplifier, there has been a problem that a sensitivity of the condenser microphone is reduced by an influence of a parasitic capacitance generated at an input terminal of the operational amplifier. This invention offers a microphone amplifier having a condenser microphone that converts a sound into a voltage signal, an operational amplifier having an inverting input terminal to which the voltage signal from the condenser microphone is applied and a non-inverting input terminal to which a direct current bias voltage is applied, a capacitor connected between the inverting input terminal and an output terminal of the operational amplifier, and a resistor connected between the inverting input terminal and the output terminal of the operational amplifier.
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Description

technical field

[0001] The present invention relates to a microphone amplifier for amplifying a voice signal from a condenser microphone for converting voice into a voltage signal, and more particularly to a microphone amplifier for reducing the influence of parasitic capacitance generated during integrated circuit integration. Background technique

[0002] Condenser microphones are known which convert sound into a voltage signal. Condenser microphones are made of capacitors. When the capacitance C of the capacitor in the formula of Q=C V (Q is the charge, C is the capacitance of the capacitor, and V is the voltage between the two ends of the capacitor) changes according to the sound, in a state of constant charge, the voltage between the two ends of the capacitor V changes, and according to this principle, sound is converted into a voltage signal.

[0003] Figure 2 shows a schematic diagram of the working principle of a condenser microphone. A capacitor microphone 10 com...

Examples

Embodiment Construction

[0019] An embodiment of the present invention will be described in detail with reference to FIG. 1 . FIG. 1 shows a microphone amplifier of a condenser microphone according to this embodiment.

[0020] Fig. 1 comprises: condenser microphone (100), and sound is transformed into voltage signal; Operational amplifier (101), inverting input terminal (-) is applied the voltage signal from this condenser microphone (100), and positive phase input terminal (+) A DC bias voltage is applied; the feedback capacitor (103) is connected between the inverting input terminal (-) and the output terminal (102) of the operational amplifier (101); the feedback resistor (104) is connected between the between the inverting input terminal (-) and the output terminal (102) of the operational amplifier (101); and a microphone bias source (105) for providing a DC bias to the capacitor microphone (100).

[0021] The two input terminals of the operational amplifier (101) have parasitic capacitances cau...