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Austriamicrosystems公司的AS3400/10/30集成了环境噪音消除（ANC）功能的扬声器放大器，能降低本底环境噪音，从而提高了手持设备，耳机，语音通信设备等的音频质量。ANC处理的带宽10-2000Hz，噪音降低10-30dB，主要用于耳机，手持设备，手机，免提卡和语音通信设备。本文介绍了AS3400/10/30主要特性，反馈和正馈方框图，反馈应用案例电路图与差分正馈应用案例电路图。 The AS3400/10/30 are speaker driver with Ambient Noise Cancelling function for handsets, headphones or ear pieces. It is intended to improve quality of e.g. music listening, a phone conversation etc. by reducing background ambient noise. The fully analog implementation allows the lowest power consumption, lowest system BOM cost and most natural received voice enhancement otherwise difficult to achieve with DSP implementations. The device is designed to be easily applied to existing architectures. An internal OTP-ROM can be optionally used to store the microphones gain calibration settings. The AS3400/10/30 can be used in different configurations for best trade-off of noise cancellation, required filtering functions and mechanical designs. The simpler feed-forward topology is used to effectively reduce low frequency background noise. The feed-back topology with either 1 or 2 filtering stages can be used to reduce noise for a larger frequency range, and to even implement transfer functions like speaker equalization, Baxandall equalization, high/low shelving filter and to set a predefined loop bandwidth. The filter loop is optimized by the user for specific handset electrical and mechanical designs by dimensioning simple R, C components. Most handset implementations will make use of a single noise detecting microphone. Two microphones could be used to allow for increased flexibility of their location in the handset mechanical design. Using the bridged mode allows to even drive high impedance headsets. AS3400/10/30主要特性： Microphone Input
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