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hearing aid circuit schematic

Hearing Aids Circuit

This is a less expensive, and DIY option for a hearing aid. It is not a substitute for a real hearing aid that an audiologist would prescribe. Amplification of all sounds and frequencies, or constant use in loud environments can cause additional hearing loss. This circuit could be helpful for some types of hearing loss and occasional use, as well as fill in during the average amount of time people wait to get a hearing aid (7 years).

This low-cost, general-purpose electronic circuit works off 3V DC (2×1.5V battery). Transistor T1 and associated components form the audio signal preamplifier for the acoustic signals picked up by the condenser microphone and converted into corresponding electrical signals.

Application

Medical grade hearing aids are very expensive, if a person needs help hearing but not necessarily the full cost and capability of a prescribed hearing aid, this might be an option.

The medium-power amplifier section is wired around popular audio amplifier IC TDA2822M (not TDA2822). This IC, specially designed for portable low-power applications, is readily available in 8-pin mini DIP package. Here the IC is wired in bridge configuration to drive the 32-ohm general-purpose monophonic earphone.

The audio output of this aid circuit is 10 to 15 mW and the quiescent current drain is below 1 mA. The circuit can be easily assembled on a veroboard. For easy assembling and maintenance, use an 8-pin DIP IC socket for TDA2822M.

Schematic of Hearing Aid Circuit

hearing aid circuit schematic

[learn_more caption=”Click here for parts list”]
RefDes Name Value Part Number Digi-Key Part Number Description
R1 RESISTOR 2.2K 6-1676481-2 A103077CT-ND RES 2.20K OHM 1/16W 0.1% 0603
R2 RESISTOR 330K ERJ-3GEYJ334V P330KGCT-ND RES 330K OHM 1/10W 5% 0603 SMD
R3 RESISTOR 680 ERJ-3GEYJ681V P680GCT-ND RES 680 OHM 1/10W 5% 0603 SMD
R4 RESISTOR 33 ERJ-3GEYJ330V P33GCT-ND RES 33 OHM 1/10W 5% 0603 SMD
C1 NON POLARIZED 0.01uF C0603X5R1A103K030BA 445-1793-1-ND CAP CER 10000PF 10V 10% X5R 0201
Q1 NPN BC547 BC547CTA BC547CTACT-ND TRANSISTOR NPN 45V 100MA TO-92
C2 NON POLARIZED 0.1uF LDEEC3100KA5N00 399-5480-1-ND CAP FILM 0.1UF 100VDC 1812
C3 POLARIZED 47uF 450-1598-ND 450-1598-ND 450-1598-ND
R5 RESISTOR 100 ERJ-3GEYJ101V P100GCT-ND RES 100 OHM 1/10W 5% 0603 SMD
R6 VARIABLE 10K EVM-3YSX50B14 P3Y103CT-ND TRIMMER 10K OHM 0.15W SMD
C4 POLARIZED 10uF EEE-1AA100NR EEE-1AA100NR CAP ALUM 10UF 10V 20% SMD
C5 NON POLARIZED 0.01uF C0603X5R1A103K030BA 445-1793-1-ND CAP CER 10000PF 10V 10% X5R 0201
U1 AMPLIFIER   TDA2822M 497-8863-5-ND IC AMP AUDIO DUAL LOW VOLT 8MDIP
C6 POLARIZED 100uF EEE-1AA101WR EEE-1AA101WR CAP ALUM 100UF 10V 20% SMD
R7 RESISTOR 4.7 ERJ-3GEYJ4R7V P4.7GCT-ND RES 4.7 OHM 1/10W 5% 0603 SMD
R8 RESISTOR 4.7 ERJ-3GEYJ4R7V P4.7GCT-ND RES 4.7 OHM 1/10W 5% 0603 SMD
C7 NON POLARIZED 0.1uF LDEEC3100KA5N00 399-5480-1-ND CAP FILM 0.1UF 100VDC 1812
C8 NON POLARIZED 0.1uF LDEEC3100KA5N00 399-5480-1-ND CAP FILM 0.1UF 100VDC 1812
SPK1 SPEAKER        
R9 RESISTOR 220 ERJ-3GEYJ221V P220GCT-ND RES 220 OHM 1/10W 5% 0603 SMD
L1 LED   VLMTG1300-GS08 VLMTG1300-GS08 LED TRUE GREEN 0603 SMD
S1 SPST   SLS121PC04 SLS121PC04 SLS121PC04
MIK1 MICROPHONE   TOM-1545P-R TOM-1545P-R MIC COND ANALOG OMNI -45DB
[/learn_more]

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