Deaf hearing aid circuit diagramDeaf hearing aid circuit diagram

This kind of hearing aid has the characteristics of high spirituality, good sound quality, low power consumption and large sound. It also has an automatic gain control function that is easy to manufacture and is suitable for patients with deafness.

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(1)Circuit principle

The figure above is the electrical schematic of the hearing aid. The sound is transmitted from the electret microphone.C,VT1,VT2The two-stage RC is amplified and finally output from the headphone.

R4For the automatic gain control resistor, it is actually a series current negative feedback resistor, which exists to make the large signal without distortion, thus maintaining good sound quality.

(2)Component selection

Electret microphoneBMuseGRz2-30type. Because the electret microphone has a field effect transistor as an amplifier, it has the advantages of high sensitivity, good frequency response, and the like, and it is an omnidirectional microphone, and all the sounds can be sent to the amplifier through it.

VTl,VT2Duplicate2SCO104(or3DX6Low noise front tube, earphone selection8ooOhmic high resistance earplug.Power supply for two sections1.5VOf5Battery.

(3)Production and debugging

Install the components in the diagram correctly on the printed circuit boardR1,MakeVTlCollector current at0.6mAabout,AdjustmentR2,MakeVT2Collector current at1. 4mALeft and right, due to the different polarization voltage of the electret microphone,

AdjustmentR1The size until the sound heard in the headphones is not distorted and the volume is at its maximum.

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