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图1所示的高灵敏度隔墙有线监听器,除了做隔墙监听外,还是一种理想的耳聋助听器,它增益高、体积小、耗电省,倍受欢迎。由驻极体话筒检测到的声音信息,经R_2、C_1和C_2加到IC_1的输入端,IC_1的放大级总增益由R_5和R_2的比例关系确定,C_2是用来改善频率特性的。R_8和R_4组成分压器模拟0状态,取电源电压的一半加到IC_1的同相端,使IC_1在单电源供电时能正常工作。Q_1、R_7组成射极跟随器,以便使高的IC_1输出阻抗与低阻耳塞相匹配。
The high-sensitivity wall-mounted wired monitor shown in Fig. 1 is an ideal deaf hearing aid besides wall-monitoring. Its high gain, small size and low power consumption make it popular. The sound information detected by the electret microphone is added to the input of IC_1 via R_2, C_1 and C_2. The overall gain of IC_1 is determined by the proportional relationship of R_5 and R_2. C_2 is used to improve the frequency characteristics. R_8 and R_4 constitute a voltage divider analog 0 state, and half of the supply voltage is applied to the noninverting side of IC_1, allowing IC_1 to function properly when powered by a single supply. Q_1, R_7 form emitter follower to match high IC_1 output impedance to low impedance earbuds.