Making hearing aids with TDA2822 ----- TDA2822 Audiphones

The hearing aid by a dual amplifier IC TDA2822 plus a small peripheral components, it popular on the market machine having an output power, a wide range of characteristics in comparison voltage, the working voltage 1.8-15V, suitable for mild deafness use. How it works: The hearing aid electrical schematic diagram shown in Figure 1. Its working principle is simple: electret microphone connected to the drain of the high-gain output circuit, and converts the external sound waves into electrical signals. Composition TDA2822 BTL amplifier circuit, the audio signal output from the microphone is amplified, and with sufficient power to promote the headphones sound. To reduce losses due to coupling, using a transformer coupling the primary affixed C2, you can filter out a portion of the induced noise, and the secondary RP is connected to control the volume. Another R1, C1 composition decoupling circuit to prevent feedback signal caused by the power source; R2, C6 frequency compensation circuit for the BTL. Audio input transformer T Replacement amplifier portable radios, such as self-wound, the core can be E14, with both primary and Φ = 0.06mm enameled wire wound 2000 turns. RP WH135 volume potentiometer employ variable resistance welded directly to the printed board. 2.5mm headphone jack socket for the horizontal two-core. As long as this circuit is assembled correctly, no debugging that is able to work properly. The power supply uses two 5th batteries, static working current is 6mA

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