Microphone amplifier circuit

Abstract

The invention provides a microphone amplifier circuit, which comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, an eighth transistor, a diode and a resistor, and is characterized in that a grid electrode of the first transistor acts as an input end of the microphone amplifier circuit, and a source electrode of the second transistor acts as an output end of the microphone amplifier circuit. The fifth transistor, the sixth transistor, the seventh transistor, the eighth transistor and the resistor form a bias circuit which is used for generating bias current and providing required current for the first transistor M1 and the second transistor M2 which act as source followers, and the second transistor M2 adopts a deep-N-well NMOS (N-channel metal oxide semiconductor) transistor to generate a back gate effect. Compared with related technologies, the microphone amplifier circuit provided by the invention has the advantages of low current consumption and high SNR (Signal to Noise Ratio).

Description

【Technical field】 [0001] The invention relates to an amplifier circuit, in particular to a microphone amplifier circuit used in MEMS technology. 【Background technique】 [0002] The microphone amplifier circuit mainly includes a MEMS sensor and an ASIC (Application-Specific Integrated Circuit, Application-Specific Integrated Circuit), both of which are electrically connected to convert sound signals into electrical signals to realize the function of the microphone. [0003] In the microphone amplifier circuit of the related art, the power supply rejection ratio (Power Supply Rejection Ratio, PSRR) of the power supply at 217 Hz determines the coupling ability of the noise from the power supply to the output, and the related microphone system using the related microphone amplifier circuit generally can only reach 66.5 dB signal-to-noise ratio (Signal-Noise-Ratio, SNR). [0004] One of the reasons for the low relative SNR is the relatively high self-noise of the relevant microp...

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Problems solved by technology

[0003] In the microphone amplifier circuit of the related art, the power supply rejection ratio (Power Supply Rejection Ratio, PSRR) of the power supply at 217 Hz determines the coupling ability of the noise from the power supply to the output, and the related microphone system using the related microphone amplifier circuit generally can only reach 66.5 dB signal-to-noise ratio (Signal-Noise-Ratio, SNR)

[0004] One of the reasons for the low relative SNR is the relatively high self-noise of the relevant microphone amplifier circuit, that is, in the 20Hz-20KHz frequency band, the noise filtered by the A-weighting (A-Weight) filter is about 3.5μVrms, and the relevant microphone system low sensitivity

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