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为了适应电化教学需要,很多大中专院校均安装上了音频感应发射系统。只要你在音频发射范围内戴上音频耳机,就能收听到教学节目。本文介绍一种用小功率音频放大器MC34119为核心构成的音频耳机,具有输出增益高、噪声低、音质效果好、性能稳定可靠等优点。 电路原理见图所示。IC是一种专用通信小功率音频放大器MC34119型。其主要性能特点:①额定工作电压范围 2～16V;②输出功率可达400mW;③负载阻抗 8～100Ω;④峰值负载电流±200mA;⑤闭环增益最大为 46dB;⑥交流输入电阻大于 30MΩ ;⑦增益带宽积 1.5MHZ;⑧工作温度范围为-20～+70℃;⑨总谐波失真不大于1％。L是一种磁性天线线圈,当空间存在音频辐射电磁波时,则会在线圈L感应得到微弱的音频信号,并经电容C_2耦合直接加到IC的输入端③脚上,进行音频功率放大。被放大后的音频信号从输出端⑤、⑧脚输出,从而使耳机EJ发出教学声。
In order to meet the needs of the electrochemical teaching, many colleges and universities are installed on the audio sensor launch system. As long as you put audio headphones in the range of audio transmission, you can listen to the teaching program. This paper introduces a low power audio amplifier MC34119 core audio headphones, with high output gain, low noise, sound quality is good, stable and reliable performance. The circuit shown in the figure. IC is a kind of special communication low-power audio amplifier MC34119 type. The main performance characteristics: ① rated working voltage range 2 ~ 16V; ② output power up to 400mW; ③ load impedance 8 ~ 100Ω; ④ peak load current ± 200mA; ⑤ closed-loop gain maximum 46dB; ⑥ AC input resistance greater than 30MΩ; ⑦ Gain bandwidth product 1.5MHZ; ⑧ operating temperature range of -20 ~ +70 ℃; ⑨ total harmonic distortion of not more than 1%. L is a kind of magnetic antenna coil. When there is audio radiation electromagnetic wave in the space, the weak audio signal is induced in the coil L and directly coupled to the input pin ③ of the IC via the capacitor C_2 for audio power amplification. The amplified audio signal from the output ⑤, ⑧ foot output, so that the headphone EJ issued a teaching sound.